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>

int main(void) {                                                                                                                                                                                  
        int n = 0;                                                                                                                                                                                
        while (1) {                                                                                                                                                                               
                scanf("%d", &n);                                                                                                                                                                  
                long ret = 1;                                                                                                                                                                     
                int i = 1;                                                                                                                                                                        
                for (; i <= n; i++) {                                                                                                                                                             
                        ret *= i;                                                                                                                                                                 
                }                                                                                                                                                                                 
                printf("%ld\n", ret);                                                                                                                                                             
        }                                                                                                                                                                                         
        return 0;                                                                                                                                                                                 
}