func checkLock(deadLocker []string, a string) bool {
    for _, s := range deadLocker {
        if a == s {
            return false
        }
    }
    return true
}

func Solution(startState string, endState string, N int, deadLocker []string) int {
    count := 0
    flag := true

    for i := 0; i < len(startState); i++ {
        diff := int(endState[i]) - int(startState[i])
        if diff != 0 {
            for diff != 0 {
                if diff > 0 {
                    diff--
                    startState = startState[:i] + string(startState[i]+1) + startState[i+1:]
                } else {
                    diff++
                    startState = startState[:i] + string(startState[i]-1) + startState[i+1:]
                }
                if checkLock(deadLocker, startState) {
                    count++
                } else {
                    flag = false
                    break
                }
            }
        }
    }

    if flag {
        return count
    } else {
        return -1
    }

}