using System;

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 public class Program{

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        public static void Main(string[] args){

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            const int TYPE_MENU = 0;

            const int TYPE_POSITIVE_INT = 1;

            const int TYPE_AMOUT_OR_INTEREST_RATE = 2;

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            Console.WriteLine("== Welcome to the financial calculator! ==");

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            while (true){

                int menu = 0;

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                while (true){

                    DisplayMenu();

                    Console.WriteLine("Enter your choice");

                    string inputMenu = Console.ReadLine();

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                    if (ValidateValue(inputMenu, TYPE_MENU)){

                        menu = int.Parse(inputMenu);

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                        if (menu == 1){

                            Console.WriteLine("===Simple interest calculator===");

                            while (true){

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                                Console.WriteLine("Enter the principal amount");

                                string inputPrincipalAmount = Console.ReadLine();

                                if (ValidateValue(inputPrincipalAmount, TYPE_AMOUT_OR_INTEREST_RATE)){

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                                    while (true){

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                                        Console.WriteLine("Enter the interest rate per time period (%): ");

                                        string inputInterestRate = Console.ReadLine();

                                        if (ValidateValue(inputInterestRate, TYPE_AMOUT_OR_INTEREST_RATE)){

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                                            while (true){

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                                                Console.WriteLine("Enter the number of time period");

                                                string inputNumTimePeriod = Console.ReadLine();

                                                if (ValidateValue(inputNumTimePeriod, TYPE_POSITIVE_INT)){

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                                                    double principalAmount = double.Parse(inputPrincipalAmount);

                                                    double interestRate = double.Parse(inputInterestRate);

                                                    int numTimePeriod = int.Parse(inputNumTimePeriod);

                                                    double finalValue = SimpleInterest(principalAmount, interestRate, numTimePeriod);

                                                    double interest = finalValue - principalAmount;

                                                    Console.WriteLine("Interest : $" + interest);

                                                    Console.WriteLine("Total amount: $" + finalValue);

                                                    break;}

                                                else{

                                                    continue;

                                                }

                                            }

                                            break;

                                        }

                                        else{

                                            continue;

                                        }

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                                    }

                                    break;

                                }

                                else{

                                    continue;

                                }

                            }

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                        }

                        else if (menu == 2){

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                            Console.WriteLine("===Compound interest calculator===");

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                            while (true){

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                                Console.WriteLine("Enter the principal amount: ");

                                string inputPrincipalAmount = Console.ReadLine();

                                if (ValidateValue(inputPrincipalAmount, TYPE_AMOUT_OR_INTEREST_RATE)){

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                                    while (true){

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                                        Console.WriteLine("Enter the interest rate per time period (%): ");

                                        string inputInterestRate = Console.ReadLine();

                                        if (ValidateValue(inputInterestRate, TYPE_AMOUT_OR_INTEREST_RATE)){

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                                            while (true){

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                                                Console.WriteLine("Enter the number of time period: ");

                                                string inputNumTimePeriod = Console.ReadLine();

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                                                if (ValidateValue(inputNumTimePeriod, TYPE_POSITIVE_INT)){

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                                                    while (true){

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                                                        Console.WriteLine("Enter the  number of compounds per time period: ");

                                                        string inputNumCompounds = Console.ReadLine();

                                                        if (ValidateValue(inputNumCompounds, TYPE_POSITIVE_INT)){

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                                                            double Principalamount = double.Parse(inputPrincipalAmount);

                                                            double interestRate = double.Parse(inputInterestRate);

                                                            int numCompounds = int.Parse(inputNumCompounds);

                                                            int numTimePeriod = int.Parse(inputNumTimePeriod);

                                                            double finalValue = FinalValueWithCompoundInterest(Principalamount,

                                                                                                               interestRate,

                                                                                                               numCompounds,

                                                                                                               numTimePeriod);

                                                            double interest = finalValue - Principalamount;

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                                                            Console.WriteLine("Interest : $" + interest);

                                                            Console.WriteLine("Total amount: $" + finalValue);

                                                        }

                                                        else{

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                                                            continue;

                                                        }

                                                        break;

                                                    }

                                                }

                                                else{

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                                                    continue;

                                                }

                                                break;

                                            }

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                                        }

                                        else{

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                                            continue;

                                        }

                                        break;

                                    }

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                                }

                                else{

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                                    continue;

                                }

                                break;

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                            }

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                        }

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                        else{

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                            Console.WriteLine("===EXIT===");

                            return;

                        }

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                    }

                    else{

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                        continue;

                    }

                    break;

                }

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            }

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        }

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        /// <summary>

        /// Calculate and return compound interest.

        /// </summary>

        /// <returns></returns>

        /// <param name="principalAmount">Principal Amount</param>

        /// <param name="ratePerPeriod">Interest rate per time period</param>

        /// <param name="numCompounds">The numver of compounds per time period</param>

        /// <param name="numPeriod">The number of time periods</param>

        public static double FinalValueWithCompoundInterest(double principalAmount,

                                                            double ratePerPeriod,

                                                            int numCompounds,

                                                            int numPeriod){

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            return principalAmount * Math.Pow((1 + (ratePerPeriod / 100) / numCompounds), numCompounds * numPeriod);

        }

        /// <summary>

        /// Calculate and return simple interest.

        /// </summary>

        /// <returns>The interest.</returns>

        /// <param name="principalAmount">Principal amount.</param>

        /// <param name="ratePerperiod">Interest rate per time period.</param>

        /// <param name="numPeriod">The Number of time period.</param>

        public static double SimpleInterest(double principalAmount, double ratePerperiod, int numPeriod){

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            return principalAmount * (1 + (ratePerperiod / 100) * numPeriod);

        }

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        /// <summary>

        /// Validates the value.

        /// </summary>

        /// <returns><c>true</c>, if value was validated, <c>false</c> otherwise.</returns>

        /// <param name="input">String to be validated</param>

        /// <param name="type">

        /// Validation Type.

        /// 0 means verification of the menu, 

        /// 1 means verification for positive integers, 

        /// 2 means verification for real numbers.

        /// 

        /// </param>

        public static bool ValidateValue(string input, int type){

            double tempDouble = 0;

            int tempInt = 0;

            bool result;

            result = double.TryParse(input, out tempDouble);

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            if (result){

                if (tempDouble < 0){

                    Console.WriteLine("Input must be at least 0.");

                    result = false;

                }

                else if (type == 0 || type == 1){ // menu, int

                    result = int.TryParse(input, out tempInt);

                    if (!result){

                        Console.WriteLine("Input must be whole number");

                        result = false;

                    }

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                    if (type == 0 && tempInt > 3){

                        Console.WriteLine("Input must be at most 3.");

                        result = false;

                    }

                }

                else if (type == 2)

                {

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                    if (tempInt < 0){

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                        Console.WriteLine("Input must be at least 0.");

                        result = false;

                    }

                }

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                return result;

            }

            Console.WriteLine("Input must be numeric");

            return result;

        }

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        /// <summary>

        /// Displaies the menu.

        /// </summary>

        public static void DisplayMenu(){

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            Console.WriteLine("1. Simple interest calculator");

            Console.WriteLine("2. Compound interest calculator");

            Console.WriteLine("3. EXIT");

        }

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    }

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}