using System;

public class Program

{

    public static void Main()

    {

        Start:

        Console.WriteLine("m =");

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

        Console.WriteLine("n =");

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

        int prod = 1;

        int i = m;

        if (m < 0 || n < 0 || m > n)

        {

            Console.WriteLine("Wrong input data!");

                goto Start;

        }

        do

        {

            prod = prod * i;

            i++;

        }

        while (i <= n);

        {

            Console.WriteLine("Equals {0}", prod);

        }

    }

}