using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        //1

    // 24/4=6

    // 25/4=6

    // 26/4=6

    // 27/4=6

    // 24%4=0

    // 25%4=1

    // 26%4=2

    // 27%4=3

    //2

    Console.WriteLine("enter amount of books:");

    int books = int.Parse(Console.ReadLine()); //get amount of books

    if(books%15!=0){ //not full shelves

        Console.WriteLine("shelves:"+((books/15)+1)+" books on last shelf: "+(books%15));

    }else{ //full shelves

        Console.WriteLine("shelves:"+(books/15));

    }

    //3

    Console.WriteLine("enter a number for a game of seven boom:");

    int num = int.Parse(Console.ReadLine()); //get a number for a game of seven boom

    if(num%7==0){ //boom

        Console.WriteLine("BOOM");

    }else{

        Console.WriteLine(num);

    }

    //4

    Console.WriteLine("sum 2 digit number:");

    int input = int.Parse(Console.ReadLine())%100; //get two digit number

    if(input>9){

        Console.WriteLine(input%10+input/10%10); //sum each digits

    }else{

        Console.WriteLine("invalid input");

    }

    Console.WriteLine("sum 3 digit number:");

    int input2 = int.Parse(Console.ReadLine())%1000; //get three digit number

    if(input2>99){

        Console.WriteLine(input2%10+input2/10%10+input2/100%10); //sum each digits

    }else{

        Console.WriteLine("invalid input");

    }

    //5

    Console.WriteLine("reverse 2 digit number:");

    input = int.Parse(Console.ReadLine())%100; //get two digit number

    if(input>9){

        Console.WriteLine(input%10+""+input/10%10+1); //reverse digits

    }else{

        Console.WriteLine("invalid input");

    }

    Console.WriteLine("reverse 3 digit number:");

    input2 = int.Parse(Console.ReadLine())%1000; //get three digit number

    if(input2>99){

        Console.WriteLine(input2%10+""+input2/10%10+""+input2/100%10+1); //reverse digits

    }else{

        Console.WriteLine("invalid input");

    }

          int n  = 345839;

    int counter = 0;

    while(n!=0){

        if(n%10==3){

            counter++;

        }

        n/=10;

    }

    Console.WriteLine("3 appears " + counter + " times");

  }

}

​

​

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