void insert(string s) {
    node *cur = root;
    for (int i = 0; i < (int) s.size(); i++) {
        if (!cur-> cld(s[i]))
            cur-> cld(s[i]) = new node;
        cur = cur-> cld(s[i]);
    }
    cur-> ex = true;
}
bool search(string s) {
    node *cur = root;
    for (int i = 0; i < (int) s.size(); i++) {
        if (!cur-> cld(s[i]))
            return false;
        cur = cur-> cld(s[i]);
    }
    return cur-> ex;
}