#include <iostream>
 
struct modulo7
{
  explicit modulo7( int i ) : number(i%7) {}
  inline int value() const { return number ; }
  private: int number ;
};
 
inline modulo7 operator+( modulo7 first, modulo7 second )
{ return modulo7( (first.value()+second.value()) % 7 ) ; }
 
inline modulo7 operator+( modulo7 first, int second )
{ return modulo7( (first.value()+second) % 7 ) ; }
 
inline modulo7 operator+( int first, modulo7 second )
{ return second + first ; }
 
template< typename stream_type > inline
stream_type& operator<< ( stream_type& stm, modulo7 m )
{ return stm << m.value() ; }
 
int main()
{
  modulo7 a(6), b(4) ;
  std::cout << a+4 << ' ' << 4+a << ' ' << a+b << '\n' ;
}