ABC283D RE

int main(int argc, char **argv)
{
    string s;
    cin >> s;
    stack<int> stck;
    vi cnt(256);
    for (int i = 0; i < s.size(); ++i) {
        if (s[i] == '(')
            stck.push(i);
        else if (s[i] == ')') {
            while (stck.empty() == false && stck.top() != '(')
                cnt[stck.top()]--, stck.pop();
            if (stck.empty() == false)
                stck.pop();
        } else {
            stck.push(s[i]);
            cnt[s[i]]++;
            if (cnt[s[i]] > 1) {
                cout << "No" << endl;
                return 0;
            }
        }
    }
    cout << "Yes" << endl;
    return 0;
};