Shared code

#include <bits/stdc++.h>

using namespace std;
using vi = vector<int>;

struct SegmentTree {
    int n;
    vi t;
    SegmentTree(vi& a) {
        n = a.size(), t.resize(4*n + 1, 0);
        for(int i = 0;i<n;++i) {
            update(1, 0, n - 1, i, a.at(i));
        }
        return;
    }
    void update(int v, int tl, int tr, int p, int x) {
        if (tl == tr) {
            t.at(v)+=x;
        }
        else {
            int tm = (tl + tr)/2;
            (p <= tm ? update(v*2, tl, tm, p, x):update(v*2 + 1, tm + 1, tr, p, x));
            t.at(v) = max(t.at(v*2), t.at(v*2 + 1));
        }
        return;
    }
    int query(int v, int tl, int tr, int x) {
        if (tl == tr) {
            return (t.at(v) >= x ? tl:-1);
        }
        int tm = (tl + tr)/2;
        return (t.at(v*2) >= x ? query(v*2, tl, tm, x):query(v*2 + 1, tm + 1, tr, x));
    }
};

int main() {
    int n, m;
    cin >> n >> m;
    vi a(n);
    for(int& v:a) {
        cin >> v;
    }
    SegmentTree T(a);
    for(int i = 0, x;i<m;++i) {
        cin >> x;
        int res = T.query(1, 0, n - 1, x);
        cout << res + 1 << ' ';
        if (res != -1) {
            T.update(1, 0, n - 1, res, -x);
        }
    }
    cout << endl;
    return 0;
}