#include <iostream>

using namespace std;

long Factorial(int n);

int main() {
   int i;
   for(i=0;i<=20;i++) {
      cout << i << "! = " << Factorial(i) << endl;
   }

   return 0;
}

long Factorial(int n) {
    if (n == 0) {
       return 1;
    }
    return n*Factorial(n-1);
}