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.

Example

Input

5


Output

120
#include <stdio.h>
int main() {long long int N,i=1;scanf("%lld",&N);while (N) i*=N--;printf("%lld\n",i);return 0;}