фенвик

#include<iostream>

using namespace std;

vector<int> t;

int get_p(int x) {
    int answ = 0;
    for (; x >= 0; x = (x & (x + 1)) - 1)
        answ += t[x];
    return answ;
}

int get(int l, int r) {
    return get_p(r) - get_p(l - 1);
}

void upd(int x) {
    for (; x < n; x |= (x + 1)) tree[x]++;
}

int main() {
    int n;
    cin >> n;
    vector<int> a(n);
    for (auto& e : a) cin >> e;
    t.assign(n, 0);
    return 0;
}