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 JavaScript (judge verdict: Accepted)

process.stdin.on("data",function(c,n,k){
	n=+(c+"").trim(),k=1;
	do{k*=n}while(--n);
	console.log(k);
}).resume();