st_query

int sumRange(int i, int j) {
    return sumQuery(i, j, 0, n - 1, 0);
}

int sumQuery(int qlo, int qhi, int clo, int chi, int i)
{
    if(qlo > chi || qhi < clo)return 0;
    if(qlo <= clo && qhi >= chi)return st[i].val;
    int mid = clo + (chi - clo) / 2;
    return sumQuery(qlo, qhi, clo, mid, 2 * i + 1) + sumQuery(qlo, qhi, mid + 1, chi, 2 * i + 2);
}