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;
typedef long long ll;
int main(){
  ll n,ans=1;
  cin>>n;
  for(ll i=n;i>=1;i--){
    ans*=i;
  }
  cout<<ans<<endl;
  return 0;
}