using System;

public class Program

{

    public static void Main()

    {

        Console.Write("Input value of N: ");

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

        int mul = 1 ;

        //Console.WriteLine();

        while (N <= 1)

        {

            Console.Write("Error! Input again: ");

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

        }

        Console.WriteLine();

        for (int i = 1; i <= N; i++ )

        {

            mul = mul * i;

        }

        Console.WriteLine("muitiplication of 1 to {0} is {1:n0}", N, mul);

    }

}