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(){
int x;
cin>>x;
long long ans=1;
for(int i=1;i<=x;i++)ans*=i;
cout<<ans<<endl;
}