using System;
using System.Collections.Generic;
using System.IO;
using System.Numerics;

class Solution {
    static void Main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution */
        int n = Convert.ToInt32(Console.ReadLine());
        BigInteger result = Factorial(n);

        Console.WriteLine(result);
    }

    public static BigInteger Factorial(int n)
    {
        BigInteger result = n;

        if ( n == 0 || n == 1) {
            return 1;
        }

        while (n > 1) {
            n--;
            result = result * n;
        }

        return result;
    }
}