package q374

func guess(num int) int { panic("stub") }

func guessNumber(n int) int {
	l, r := 1, n+1

	for l < r {
		m := (l + r) / 2
		switch guess(m) {
		case -1: // too high
			r = m
		case 1: // too low
			l = m + 1
		case 0:
			return m
		}
	}
	return -1
}

var _ = guessNumber