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,ans=1;
cin >> n;
for(long long int i=1;i<=n;i++){
ans*=i;
}
cout << ans << "\n";
return 0;
}