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;

static class Factrial
{
    static void Main()
    {
        var f = Enumerable.Range( 1, int.Parse( Console.ReadLine() ) )
            .Aggregate( (x, y) => x * y );
        Console.WriteLine( f );
    }
}