#include <iostream>

using namespace std;
int main() {
    size_t n_letters, n_cookies=0;
    cin >> n_letters;
    char prev, curr;
    cin >> curr;
    for (size_t i = 1; i < n_letters; ++i) {
        prev = curr;
        cin >> curr;
        n_cookies += ((prev == '(' && curr == ')') || (prev == ')' && curr == ')'));
    }
    cout << n_cookies << endl;
    return 0;
}