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<bits/stdc++.h>
using namespace std;
int main()
{
long long int n, sum=1;
cin>>n;
for(int i=2; i<=n; i++){sum*=i;}
cout<<sum<<endl;


return 0;
}
