void main() {
  String s = "([}}])";
  print(Solution().isValid(s));
}

class Solution {
  bool isValid(String s) {
    List<String> stack = [];
    if (s.length % 2 != 0) {
      return false;
    }
    for (int i = 0; i < s.length; i++) {
      if (s[i] == '{' || s[i] == '[' || s[i] == '(') {
        stack.add(s[i]);
      } else if (s[i] == "}" && stack.isNotEmpty && stack.last == '{') {
        stack.removeLast();
      } else if (s[i] == "]" && stack.isNotEmpty && stack.last == '[') {
        stack.removeLast();
      } else if (s[i] == ")" && stack.isNotEmpty && stack.last == '(') {
        stack.removeLast();
      } else
        return false;
    }
    return stack.isEmpty;
  }
}