package main

import "sort"

func BinarySearch(s []string, k string) int {
	sort.Strings(s)
	lo, hi := 0, len(s)-1
	for lo <= hi {
		m := (lo + hi) >> 1
		if s[m] < k {
			lo = m + 1
		} else if s[m] > k {
			hi = m - 1
		} else {
			return m
		}
	}
	return -1
}