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;
using System.Collections.Generic;
using System.Linq;

class Program {

    static int Main(string[] args) {
        //List<int> list = new List<int>();

        string v = Console.ReadLine();
        //string[] vs = v.Split(' ');

        int n = int.Parse(v);

        int x = n;
        for (int i = n - 1; i >= 1; i--) {
            x = x * i;
        }
        Console.WriteLine(x);

        return 0;
    }
}