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 JAVA (judge verdict: Accepted)

import java.io.*;
public class Main {
	public static void main(String[] args) throws IOException {
		System.out.println((new Main()).fact(Integer.parseInt((new BufferedReader(new InputStreamReader(System.in))).readLine())));}
	private long fact(long n){return (n==0)?1:n*fact(n-1);}
}