#include <iostream>

using namespace std;

int main(){
    
    int num,fact=1;

    cout<<" Enter Number:  ";

    cin>>num;

if (num <=20){

          for(int a=1;a<=num;a++){
                  fact = fact * a;
                                  }

    cout<<fact<<endl;
    }
else
    cout<<"none";
   return 0;
   
}