func getHint(secret string, guess string) string {
	s, g := make([]int, 10), make([]int, 10)
	bulls, cows := 0, 0
	for i := range secret {
		if secret[i] == guess[i] {
			bulls++
		} else {
			s[int(secret[i]-'0')]++
			g[int(guess[i]-'0')]++
		}
	}
	for i := 0; i < 10; i++ {
		if s[i] < g[i] {
			cows += s[i]
		} else {
			cows += g[i]
		}
	}
	return fmt.Sprintf("%dA%dB", bulls, cows)
}