Problem:
Factorial

Write a program which reads an integer n and prints the factorial of n. You can assume that n ≤ 20.

Input

An integer n (1 ≤ n ≤ 20) in a line.

Output

Print the factorial of n in a line.

Sample Input

5

Output for the Sample Input

120

Solution in C# (judge verdict: Wrong Answer)

using System;

namespace _0019
{
    class Program
    {
        public static int fact(int n)
        {
            if (n == 0)
            {
                return 1;
            }
            return n * fact(n - 1);
        }
        public static void Main()
        {
            int n = int.Parse(Console.ReadLine());
            Console.WriteLine(fact(n));
            Console.ReadLine();
        }
    }
}