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.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;

public class Main {

	public static void main(String[] args) throws NumberFormatException, IOException {

		String strLine ="";
		BufferedReader stdReader =
				new BufferedReader(new InputStreamReader(System.in));

		int MAX_DETASET  = 20;
		int cnt = 0;

		ArrayList<String> list = new ArrayList<String>();



		if((strLine = stdReader.readLine()) != null) {

		//??°????????????
		long intStrLine = Integer.parseInt(strLine);
		long k = intStrLine;

		for(long i = intStrLine -1; i > 0 ; i--){
			k = k * i;
		}

		System.out.println(k);


		}

	}

}