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 n,sum=1;
cin>>n;
for(int k=1;k<=n;k++){
	sum=sum*k;
}
cout<<sum<<endl;

	return 0;
}