Shared code

#include <bits/stdc++.h>

template <typename T> class SegmentTree {
public:
  int n;
  T idt;
  std::vector<T> seg;
  std::function<T(T, T)> f;

  SegmentTree(int n, std::function<T(T, T)> f = std::plus<T>(), T idt = T()) : n(n), idt(idt), f(f), seg(2 * n, idt) {}

  void set(int idx, T x) {
    for (seg[idx += n] = x, idx /= 2; idx > 0; idx /= 2) {
      seg[idx] = f(seg[2 * idx], seg[2 * idx + 1]);
    }
  }

  T query(int l, int r) {
    T ansL = idt, ansR = idt;
    for (l += n, r += n + 1; l < r; l /= 2, r /= 2) {
      if (l & 1) ansL = f(ansL, seg[l++]);
      if (r & 1) ansR = f(seg[--r], ansR);
    }
    return f(ansL, ansR);
  }

  int partition_point(int l, const std::function<bool(T)> &t) {
    T p = idt;
    for (l += n; t(f(p, seg[l])) and l; l /= 2) {
      if (l & 1 and l != 1) p = f(p, seg[l++]);
    }
    if (!l) {
      return n;
    }
    while (l < n) {
      if (t(f(p, seg[l <<= 1]))) p = f(p, seg[l++]);
    }
    return l - n;
  }
};

int main() {
  std::ios_base::sync_with_stdio(false);
  std::cin.tie(nullptr);

  const int64_t inf = 1e15;

  int n, m;
  std::cin >> n >> m;
  SegmentTree<int64_t> st(n, [&](int64_t a, int64_t b) {
    return std::max(a, b);
  }, -inf);
  for (int i = 0, e; i < n; ++i) {
    std::cin >> e;
    st.set(i, e);
  }

  while (m--) {
    int r;
    std::cin >> r;
    int idx = st.partition_point(0, [&](int64_t max) {
      return max < r;
    });
    if (idx == n) {
      idx = -1;
    }
    std::cout << idx + 1 << ' ';
    if (idx != -1) {
      st.set(idx, st.query(idx, idx) - r);
    }
  }
  std::cout << '\n';
}