Скобочное выражение

input_string = input()
left_bracket = list()
right_bracket = list()
counter = 0
for i in input_string:
    if i == "(" or i == "[":
        if right_bracket:
            if right_bracket[-1] == "]" and i == "[":
                right_bracket.pop()
            elif right_bracket[-1] == "]" and i == "(":
                right_bracket.pop()
                counter += 1
            elif right_bracket[-1] == ")" and i == "(":
                right_bracket.pop()
            elif right_bracket[-1] == ")" and i == "[":
                right_bracket.pop()
                counter += 1
        else:
            left_bracket.append(i)
    else:
        if left_bracket:
            if left_bracket[-1] == "[" and i == "]":
                left_bracket.pop()
            elif left_bracket[-1] == "[" and i == ")":
                left_bracket.pop()
                counter += 1
            elif left_bracket[-1] == "(" and i == ")":
                left_bracket.pop()
            elif left_bracket[-1] == "(" and i == "]":
                left_bracket.pop()
                counter += 1
        else:
            right_bracket.append(i)
if len(right_bracket) == 0 and len(right_bracket) == 0:
    print(counter)
else:
    print(-1)