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 <iostream>
using namespace std;

//0019
int main(){
	long long int x, f;

	cin >> x;
	f=x;
	while(--x){
		f*=x;
	}
	cout << f <<endl;
	return 0;
}