#include <iostream.h>
#include <stdlib.h>
void main()
{
	float num;
	float fact(float);

	cout << "Enter a number";
	cin >> num;
	if ( num < 0 ) exit(0);
	cout << "The answer is " << fact(num) << endl;
}

float fact(float num)
{
	float ans;
	if (num == 0) 
		return 1;
	else
	{   ans = num*fact(num-1);
        cout << num << "!= " << ans << endl;
		return ans;
	}
}