#include <bits/stdc++.h>
using namespace std;
using R = vector<int>;

R mn(R r1, R r2) {
    int a = r1[0], b = r1[1], s1 = r1[2], c = r2[0], d = r2[1], s2 = r2[2];
    return {min(a, c), b + d - 1, s1 + s2};
}

R mx(R r1, R r2) {
    int a = r1[0], b = r1[1], s1 = r1[2], c = r2[0], d = r2[1], s2 = r2[2];
    R r = mn({s1 + 1 - b, s1 + 1 - a, s1}, {s2 + 1 - d, s2 + 1 - c, s2});
    r[0] = s1 + s2 + 1 - r[0];
    r[1] = s1 + s2 + 1 - r[1];
    return r;
}

R f(string& s, vector<vector<int>>& sum, int x, int y, int cnt) {
    if (x == y) return {1, 1, 1};
    int type = 0;
    if (s[x + 1] == 'a') type++;
    auto it = upper_bound(sum[cnt].begin(), sum[cnt].end(), x);
    if (it == sum[cnt].end() || *it >= y) {
        if (type) return {2, 2, 2};
        else return {1, 1, 2};
    }
    else if (*it + 1 == y) {
        if (type) return mx({1, 1, 1}, f(s, sum, x + 6, y - 1, cnt + 1));
        else return mn({1, 1, 1}, f(s, sum, x + 6, y - 1, cnt + 1));
    }
    else {
        if (type) return mx(f(s, sum, x + 4, *it, cnt + 1), f(s, sum, *it + 2, y - 1, cnt + 1));
        else return mn(f(s, sum, x + 4, *it, cnt + 1), f(s, sum, *it + 2, y - 1, cnt + 1));
    }
}

int main() {
    string s; cin >> s;
    int n = s.size();
    vector<vector<int>> sum(n);///
    int cnt = 0;
    for (int i = 0; i < n; ++i) {
        if (s[i] == '(') cnt++;
        if (s[i] == ')') sum[--cnt].push_back(i);
    }
    R r = f(s, sum, 0, n - 1, 1);
    cout << r[1] - r[0] + 1;
}