template <typename T>
vector<int> manacher(const vector<T>& s, const T& never) {
    vector<T> t = { never };
    for (auto&& c : s) {
        t.emplace_back(c);
        t.emplace_back(never);
    }
    int n = t.size();
    vector<int> r(n);
    for (int i = 0, j = 0; i < n; ++i) {
        if (2 * j - i >= 0 && j + r[j] > i) {
            r[i] = min(r[2 * j - i], j + r[j] - i);
        }
        while (i - r[i] >= 0 && i + r[i] < n && t[i - r[i]] == t[i + r[i]]) {
            r[i] += 1;
        }
        if (i + r[i] > j + r[j]) {
            j = i;
        }
    }
    for (int i = 0; i < n; i += 2) {
        r[i] = (r[i] - 1) / 2;
    }
    for (int i = 1; i < n; i += 2) {
        r[i] /= 2;
    }
    return r;
}