Overload unary minus operator - C++ Program

#include<iostream>
using namespace std;

class Numbers
{
        int x, y, z;
    public:
        void accept()
        {
                cout<<"\n Enter Three Numbers";
                cout<<"\n --------------------------";
                cout<<"\n First Number   :  ";
                cin>>x;
                cout<<"\n Second Number  :  ";
                cin>>y;
                cout<<"\n Three Number   :  ";
                cin>>z;
                cout<<"\n --------------------------";
        }
        void display()
        {
                cout<<" ";
                cout<<x<<"\t"<<y<<"\t"<<z;
        }
        void operator-()
        {
                x=-x;
                y=-y;
                z=-z;
        }
};
int main()
{
        Numbers num;
        num.accept();
        cout<<"\n Numbers are :\n\n";
        num.display();
        -num;    //Overloaded Unary (-) Operator
        cout<<"\n\n Negated Numbers are :\n\n";
        num.display();
        return 0;
}