Re: ambiguous overload

#include<iostream>
using namespace std;
class Integer{
        int i;
        public:
                Integer(int ii):i(ii){}
                const Integer operator+(const Integer& rv){
                        cout<<"1-operator+"<<endl;
                        return Integer(i+rv.i);
                }
                Integer operator+=(Integer rv){
                        i+=rv.i;
                        cout<<"2-operator+="<<endl;
                        return *this;
                }
                friend Integer& operator+(Integer,Integer);

                void display(){
                        cout<<"3-display()// i="<<i<<endl;
                }
};
Integer& operator+(Integer rv,Integer rs ){
                        cout<<"2-operator+="<<endl;
        rv.i+=rs.i;
        return rv;

What should I do to prevent this ??