package q69

func mySqrt(x int) int {
	if x < 2 {
		return x
	}
	l, r := 0, x/2+1
	for l < r {
		m := (l + r) / 2
		sq := m * m
		switch {
		case sq == x:
			return m
		case sq < x:
			if (m+1)*(m+1) > x {
				return m
			}
			l = m + 1
		case sq > x:
			r = m
		}
	}
	return -1
}

var _ = mySqrt