// find the first index in the range [ql, qr] which is >= height[ind]
    long long queryr2(int node, int nl, int nr, int ql, int qr, int ind) {
        // check if the current one is in range
        if (nr < ql || nl > qr)
            return -1;

        // check if the range has a tall enough value
        if (seg[node] < height[ind])
            return -1;

        // at this point, we are guaranteed the answer is in this range

        if (nl == nr) {
            return nl;
        }

        int mid = (nl+nr)/2;

        int left_query = queryr2(node*2, nl, mid, ql, qr, ind);

        if (left_query == -1)
          return queryr2(node*2+1, mid+1, nr, ql, qr, ind);
        else
          return left_query;

    }