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>

long kai(long i){
		if(i==1||i==0){
			return 1;
		}
		return i*kai(i-1);
	}
int main(){

	long n;
	scanf("%ld",&n);

	printf("%ld\n",kai(n));
	return 0;

}