using System;

public class Program

{

    public static void Main()

    {

/*

Create a console application that uses a (1) while and (2) a for loop to calculate the product of the first 10 and 20 integer numbers. 

Start at 1.

You will write 2 while and 2 for loop statements. 

*/

        // A for loop to calculate the product of first 10 numbers starting at 1

        // if it is a sum, start should be 0 but multiplying case, it should be 1 

        int i;

        int product = 1;

        int n = 10;

        for (i =1; i <= n; i++)

        {

            product *= i;

        }

        // Writeliine

        Console.WriteLine ("1-a. (Using Loop) Product of first {0} number is {1}", n, product);

        // Use While to calculate the product of first 10 numbers starting at 1

        product = 1;

        int end = 10; //why does professor not define end as an "int"?

        i = 1;

        while (i <= end)

        {

            product *= i;

            i++;

        }

        Console.WriteLine("1-b. (Using While) Product of first {0} number is {1}", end, product);

​

        // A for loop to calculate the product of first 20 numbers starting at 1

        // if it is a sum, start should be 0 but multiplying case, it should be 1 

        // final product should be defined as "Long" type, integer is not enough for this. (it turns "-"value if defined as "int")

        int k;

        long final = 1;

        int n2 = 20;

        for (k =1; k <= n2; k++)

        {

            final *= k;

        }

        // Writeliine

        Console.WriteLine ("2-a. (Using Loop) Product of first {0} number is {1}", n2, final);

        // Use While to calculate the product of first 10 numbers starting at 1

        final = 1;

        k=1;

        while (k <= n2)

        {

            final *= k;

            k++;

        }

        Console.WriteLine("2-b. (Using While) Product of first {0} number is {1}", n2, final);

/*

2. For the Gauss in you: Given m=1777 and n=2022, what is the sum of the numbers between m and n (both included in the sum)?

​

Add this for loop to your program above.

As a brain teaser (not required to solve), see slide #12 to find inspiration to derive a formula for this problem.

*/

        int a;

        int b = 2022;

        int total = 0;

        for (a=1777; a<=b; a++)

        {

            total += a;

        }

        Console.WriteLine("Extra. The sum of the numbers between {0} and {1} are {2}",a,b,total);

    }

}