Overloaded << Operator Error ?? why

#include<iostream.h>

//prefix and postfix Operator overloading // Inorder to see effect
overload operator <<

class A
{
  public :
  int i,j;
  A(int _i,int _j):i(_i),j(_j){}
  A & operator++();
  const A operator++(int);

};


A& A::operator++()
{
  this->i = this->i + 1;
  this->j = this->j +1 ;
  return *this;
}



const A A::operator++(int)
{
 A obj = *this;
 this->i = this->i + 1;
 this->j = this->j +1 ;

 return obj;
}

ostream & operator << (ostream & out ,  A & obj)
{
   out<<"Value of i  "<<obj.i<<endl;
   out<<"Value of j  "<<obj.j<<endl;
   return out;
}

int main()
{

A obj(10,20);
cout<<++obj;
cout<<obj++;  // Error Why ????????????????

return 0;
}