void add(node *&cur, node *&v) {
    if(cur -> y < v -> y) {
        if(cur -> right != nullptr) {
            v -> left = cur -> right;
            parent[v -> left -> num] = v -> num;
        }
        cur -> right = v;
        parent[v -> num] = cur -> num;
        return;
    }
    else {
        if(parent[cur -> num] == -1) {
            v -> left = cur;
            parent[cur -> num] = v -> num;
            return;
        }
        else {
            add(nodes2[parent[cur -> num]], v);
        }
    }
}