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