模板：树状数组

inline int lowbit(int x) { return x & -x; }
int tr[N], n;
void update(int u, int val) {
    while (u <= n) {
        tr[u] += val, u += lowbit(u);
    }
}
int query(int u) {
    int res = 0;
    while (u) res += tr[u], u -= lowbit(u);
    return res;
}