Could you please tell me what I am doing wrong? I am trying to overload the + operator, and output the sum of the 5 numbers (a, b, c, d, e).

Code:

#include <iostream.h>
#include <math.h>
class BigInteger{
private:
public:
double a, b, c, d, e;
void initial();
//sum(BigInteger &one, BigInteger &two);
friend BigInteger operator+(BigInteger);
};
void BigInteger::initial()
{
cout << "Please enter 5 integers: " ;
cin >> a >> b >> c >> d >> e;
}
BigInteger operator+(BigInteger &num)
{
//BigInteger num;
num = ; // what do I put here???
return num;
}
int main()
{
BigInteger one, two;
one.initial();
cout << one.a << one.b << one.c << one.d << one.e <<endl;
return 0;
}