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: Time Limit Exceeded)

#include<stdio.h>
main(){long long n,i;scanf("%d",&n);for(i=n;--n;)i*=n;printf("%d\n",i);}