int check_if_correct(const std::string& str) {
    std::vector<char> stack;
    for (size_t i = 0; i < str.length(); ++i) {
        if (str[i] == '(' || str[i] == '[' || str[i] == '{') {
            stack.push_back(str[i]);
            continue;
        }
        if (str[i] == ')') {
            if (stack.empty() || stack.back() != '(') {
                return i;
            }
            stack.pop_back();
            continue;
        }
        if (str[i] == ']') {
            if (stack.empty() || stack.back() != '[') {
                return i;
            }
            stack.pop_back();
            continue;
        }
        if (str[i] == '}') {
            if (stack.empty() || stack.back() != '{') {
                return i;
            }
            stack.pop_back();
            continue;
        }
    }
    return stack.empty() ? -1 : stack.size();
}