const int maxn = (int)1e5 + 10;
vector <int> ed[maxn];

int hospital(int city_nodes, vector<int> city_from, vector<int> city_to) {
    int n = city_nodes;
    for (int i = 0; i < (int)city_from.size(); i++) {
        int x = city_from[i];
        int y = city_to[i];
        x--;
        y--;

        ed[x].push_back(y);
        ed[y].push_back(x);
    }

    int ans = n;

    for (int ms = 0; ms < (1 << n); ms++) {
        int cur = 0;
        for (int i = 0; i < n; i++) {
            if ((ms >> i) & 1) {
                cur++;
                continue;
            }

            bool ok = false;

            for (int j = 0; j < (int)ed[i].size(); j++) {
                int to = ed[i][j];

                if ((ms >> to) & 1) {
                    ok = true;
                    break;
                }
            }

            if (!ok) {
                cur = n;
                break;
            }
        }

        ans = min(ans, cur);
    }

    return ans;
}