package q1117

type void struct{}

type H2O struct {
	h, o, hRel chan void
}

func NewH2O() *H2O {
	h := &H2O{
		h:    make(chan void, 2),
		o:    make(chan void, 2),
		hRel: make(chan void, 2),
	}
	h.o <- void{}
	return h
}

func (h *H2O) Hydrogen(releaseHydrogen func()) {
	<-h.h
	// releaseHydrogen() outputs "H". Do not change or remove this line.
	releaseHydrogen()

	h.hRel <- void{} // confirmation
}

func (h *H2O) Oxygen(releaseOxygen func()) {
	<-h.o

	// releaseOxygen() outputs "H". Do not change or remove this line.
	releaseOxygen()

	h.h <- void{}
	h.h <- void{}
	<-h.hRel
	<-h.hRel
	h.o <- void{}
}