Factorial

using System;
using System.Numerics;


class MainClass
{
    static void Main()
    {
        BigInteger  num = BigInteger.Parse(Console.ReadLine());
        FactorialCalc(num);
    }

    static void FactorialCalc(BigInteger  num)
    {
        BigInteger sum = num;
        for (BigInteger i = num - 1 ; i >= 1; i--)
        {
            sum *= i;
        }
        Console.WriteLine(sum);
    }
}