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;

int main() {
	long long int n, f=1;
	cin>>n;
	for (int i=1; i<=n; i++)
		f*=i;
	cout<<f<<endl;
	return 0;
}