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<cstdio>

int main(){
	long long n,a = 1;
	scanf("%ld", &n);
	while(n){
		a *= n;
		n--;
	}
	printf("%ld\n", a);
	return 0;
}