#include <iostream>

struct Node {
  int x;
  Node *next = nullptr;
  Node *prev = nullptr;
  explicit Node(int x) : x(x) {
  }
};

struct Stack {
  int size = 0;
  Node *begin = nullptr;
  Node *cur = nullptr;
  void PushBack(int x) {
    ++size;
    if (begin == nullptr) {
      cur = new Node(x);
      begin = cur;
    } else {
      auto new_cur = new Node(x);
      cur->next = new_cur;
      new_cur->prev = cur;
      cur = new_cur;
    }
  }
  void PopBack() {
    --size;
    auto new_cur = cur->prev;
    delete cur;
    cur = new_cur;
  }
  int Back() const {
    return cur->x;
  }
  int Size() const {
    return size;
  }
};

void Clean(Stack &a) {
  auto cur = a.cur;
  while (cur != nullptr) {
    auto prev = cur->prev;
    delete cur;
    cur = prev;
  }
}

int main() {
  Stack t;
  char c;
  int cnt = 0;
  while (std::cin >> c) {
    if (t.Size() > 0 and t.Back() == '(' and c == ')') {
        t.PopBack();
    } else if (c == '(') {
        t.PushBack(c);
    } else {
        cnt++;
    }
  }
  std::cout << cnt + t.Size() << '\n';
  Clean(t);
}