#include <iostream>
using namespace std;

double factorial(int n);

int main()
{
  int n;

  while ( 1 ) {
    cout << "Number to compute factorial?";
    cin >> n;
    if ( n == -3 ) break;
    cout << n << "! = " << factorial(n) << endl;
  }
  return 0;
}

double factorial(int n){
  if ( n <= 0 ) return (1.0);
  else
    return ((double)n*factorial(n-1));
}