Checking Unary Minus Operator

#include<iostream.h>
#include<conio.h>
class unary
{
  int a,b,c;
 public:
    void get(int a1,b1,c1)
 {
    a=a1;b=b1;c=c1;
 }
 void operator -()
{
  a=-a;
  b=-b;
  c=-c;
}
void disp()
{
  cout<<"Value of A is :"<<a<<endl;
  cout<<"Value of B is :"<<b<<endl;
  cout<<"Value of C is :"<<c<<endl;
}    
};

int main()
{
 int x,y,z;
 clrscr();
cout<<"Unary Minus Operator"<<endl;
cout<<"------- -------- -----------"<<endl;
cout<<"Enter Three Numbers :"<<endl;
cin>>x;
cin>>y;
cin>>z;
unary ob;
ob.get(x,y,z);
cout<<"Before Operator Overloading"<<endl;
cout<<"-------- ----------- ---------------"<<endl;
 ob.disp();
 cout<<endl;
 -ob;
cout<<"After Operator Overloading"<<endl;
cout<<"------ ----------- ---------------"<<endl;
  ob.disp();
  cout<<endl;
getch();
}