1function lowbit(x) { return x & (-x); }
2function update(tree, n, i, delta) {
3 while (i <= n) {
4 tree[i] += delta;
5 i += lowbit(i);
6 }
7}
8function query(tree, i) {
9 let sum = 0;
10 while (i > 0) {
11 sum += tree[i];
12 i -= lowbit(i);
13 }
14 return sum;
15}