Barok (nedovrseno) {err: segfault}

#include <bits/stdc++.h>
using namespace std;

struct k {
    int r, c;
};

int main() {
    int l, w, n, bn, cnt = 0;
    cin >> l >> w >> n >> bn;
    vector<k> bk;
    vector<set<int>> done;
    for (int i = 0; i < bn; ++i) {
        int r, c;
        cin >> r >> c;
        r -= 1;
        c -= 1;
        bk.push_back({r, c});
        done[r].insert(c);
    }
    int op[4][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
    while (cnt < n) {
        for (auto it = bk.begin(); it != bk.end(); ++it) {
            k b = *it;
            bk.erase(it);
            for (int j = 0; j < 4; ++j) {
                int r = b.r + op[j][0];
                int c = b.c + op[j][1];
                if (!(r == l || r < 0 || c == w || c < 0) && done[r].find(c) == done[r].end()) {
                    cnt++;
                    bk.push_back({b.r, b.c});
                    done[r].insert(c);
                }
            }
        }
    }
    cout << cnt;
}