using System;

public class Program

{

    public static void Main()

    {

        // defines variables prod, number, i

        int prod = 1;

        int number = 1;

        int i;  

        //while 10

        while (number <= 10)

        {

            prod = prod * number;

            number++;

        }

        Console.WriteLine("The product of the first 10 numbers is: " + prod);

        // do while 20

        do 

        {

            prod = prod * number;

            number++;

        } while (number <= 20);

        Console.WriteLine("The product of the first 20 numbers is : " + prod); 

        //for  50

        for(i=1; i <= 50; i++) 

        { 

            prod = prod * i;       

        } 

        Console.WriteLine("The product of the first 50 numbers is : " + prod); 

        //while 100

        while (number <= 100)

        {

            prod = prod * number;

            number++;

        }

        Console.WriteLine("The product of the first 100 numbers is: " + prod); 

        //while 1000

        while (number <= 1000)

        {

            prod = prod * number;

            number++;

        }

        Console.WriteLine("The product of the first 1000 numbers is: " + prod); 

    }

}