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