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.math.*;
import java.text.*;
import java.lang.*;
import java.util.*;
public class Main {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		while(in.hasNext()){
			int n = in.nextInt();
			System.out.println(fact(n));
		}
	}

	private static BigInteger fact(int n){
		if(n==0) return BigInteger.ONE;
		return (new BigInteger(new Integer(n).toString()).multiply(fact(n-1)));
	}
}