Problem with copy constructor

Hi,

I have this working program (see first program below) that works
without an explicit copy constructor:

//--------------------------- start of first program
-----------------------------//

#include <iostream>

using namespace std;

class Complex
{
   public:
     Complex() { real = 0 ; imag = 0 ; }  		// default constructor
     Complex(int r, int i);                     // convert constructor

     // overload the following operators
     Complex operator - ()  ;     // unary negation

     int real;
     int imag;
};

int main () {

	Complex x(1,8); // input is 1+8i
	Complex z     ; // output should be -1 + -8i

	z=-x;
	cout << z.real << " + " << z.imag <<"i";
}

Complex::Complex(int r, int i): real(r), imag(i) {}

Complex Complex::operator- () {
	return Complex(-real, -imag);
}

// --------------------- end of first program
------------------------- //

The error occurs when I added a copy constructor (see second program
below).

//------------------- start of second program ----------------------//

#include <iostream>

using namespace std;

class Complex
{
   public:
     Complex() { real = 0 ; imag = 0 ; }  		// default constructor
     Complex (Complex &) ;   			// added copy constructor
     Complex(int r, int i);                     // convert constructor

     // overload the following operators
     Complex operator - ()  ;     // unary negation

     int real;
     int imag;
};

int main () {

	Complex x(1,8); // input is 1+8i
	Complex y(x);
	Complex z     ; // output should be -1 + -8i

	z=-x;
	cout << z.real << " + " << z.imag <<"i";
}

Complex::Complex(int r, int i): real(r), imag(i) {}

Complex::Complex(Complex & copy): real(copy.real), imag(copy.imag) {}

Complex Complex::operator- () {
	return Complex(-real, -imag);
}

//------------------------ end of second program
------------------------------//

Please help.

Thank you.