using System;

public class Program

{

    public static void Main()

    {

        Console.Write("n = ");

        int n = int.Parse(Console.ReadLine());

        Console.Write("m = ");

        int m = int.Parse(Console.ReadLine());

​

        int num = n;

        long product = 1;

        do

        {

            product *= num; num++;

        }

        while (num <= m);

        Console.WriteLine("product[n...] = " + product);

    }

}