enum Signal { Go, Caution, Stop } ;

class StopLight {
public:
	StopLight() ;
	int bulbNSR()  ;
	int bulbNSY() ;
	int bulbNSG() ;
	int bulbEWR() ;
	int bulbEWY() ;
	int bulbEWG() ;
	void Tick() ;
private:
	int time ;
	Signal stateNS ;
	Signal stateEW ;
} ;