#include <iostream>
#include <list>
#include <queue>
#include <vector>

using namespace std;

struct SegLengthPos {
    int length;
    int beg_pos;
    int operation_idx;
};

bool operator< (const SegLengthPos& lhs, const SegLengthPos& rhs) {
    if (lhs.length != rhs.length) return lhs.length > rhs.length;
    return lhs.beg_pos < rhs.beg_pos;
}

int main() {
    list<SegLengthPos> l;

    auto comparator = [](const list<SegLengthPos>::iterator& lhs, const list<SegLengthPos>::iterator& rhs) {
        return *lhs < *rhs;
    };

    priority_queue <list<SegLengthPos>::iterator,
        vector<list<SegLengthPos>::iterator>, decltype(comparator)> pq(comparator);

    int memory_cells_count, requests_count;
    cin >> memory_cells_count >> requests_count;

    vector<list<SegLengthPos>::iterator> history(1 + requests_count);

    l.push_back({ memory_cells_count, 1 });
    pq.push(l.begin());

    for (int i = 1; i <= requests_count; ++i) {
        int operation;
        cin >> operation;

        if (operation > 0) {
            if (pq.top()->length < operation) {
                history[i] = l.end();
                cout << -1;
            } else {
                auto seg_data = *pq.top();
                auto it = l.erase(pq.top());
                pq.pop();
                if (it != l.end()) prev(it);
                auto it1 = l.insert(it, { seg_data.length - operation, seg_data.beg_pos + operation, i});
                pq.push(it1);

                history[i] = it1;
                cout << seg_data.beg_pos << '\n';
            }
            continue;
        }

        if (history[operation] == l.end()) continue;

        auto it = history[operation];
        auto [len, pos, op_odx] = *history[operation];
        history[operation] = l.end();

        auto l_it = it;
        auto r_it = it;
        if (l_it != l.begin()) prev(l_it);
        if (r_it != l.end()) next(r_it);

        if (r_it != l.end() && it->beg_pos + it->length == r_it->beg_pos) {
            it->length += r_it->length;
            history[r_it->operation_idx] = l.end();
            l.erase(r_it);
        }
        if (l_it != it && l_it->beg_pos + l_it->length == it->beg_pos) {
            l_it->length += it->length;
            history[it->operation_idx] = l.end();
            l.erase(it);
        }
    }

    return 0;
}