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(){
	int i;
	long long sum=1;
	scanf("%d",&i);
	for(;i>1;i--)sum*=i;
	printf("%lld\n",sum);
	return 0;}
