/****************************************************************************
** COPYRIGHT (C):    1996 Cay S. Horstmann. All Rights Reserved.
** PROJECT:          Computing Concepts with C++
** FILE:             fac.cpp
** UPDATED:          RJB Thu May  2 11:13:52 PDT 2002
****************************************************************************/

#include <iostream>
#include <cassert>
long factorial(int n)
{	assert(n >=0 );
	if (n == 0)
		return 1;
	else
	{  long result = n * factorial(n - 1);
		return result;
	}
}
int main()
{	cout << "Please enter a number: ";
	int n;
	cin >> n;
	cout << n << "! = " << factorial(n) << "\n";
	return 0;
}