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;

class Program
{
	static void Main()
	{

		int n = int.Parse(Console.ReadLine());
		int sum = n;

		for (int i = n; i >= 1; i--)
		{
			sum = sum * i;
		}

		Console.WriteLine(sum);
	}
}