int segment_tree_size;
vector<int> segment_tree;

void change(int point, int value){
    point += segment_tree_size - 1;
    segment_tree[point] = value;
    while(point){
        point = (point - 1) / 2;
        segment_tree[point] = segment_tree[point * 2 + 1] + segment_tree[point * 2 + 2];
    }
}

int range_sum(int left, int right, int now, int point_left, int point_right){
    if(right <= point_left || point_right <= left){
        return 0;
    }else if(left <= point_left && point_right <= right){
        return segment_tree[now];
    }else{
        return range_sum(left, right, now * 2 + 1, point_left, (point_left + point_right) / 2) +
               range_sum(left, right, now * 2 + 2, (point_left + point_right) / 2, point_right);
    }
}