void bfs(int v) {
    queue<int> q;
    q.push(v);
    while (!q.empty()) {
        v = q.front();
        q.pop();
        for (auto u: ng[v]) {
            if (d[u] > d[v] + 1) {
                d[u] = d[v] + 1;
                q.push(u);
            }
        }
    }
}

d.assign(comp, INF);
for (int i = 0; i < comp; i++) {
    if (d[i] == INF) {
        d[i] = 0;
        bfs(i);
    }
}
int start = 0;
vector<int> check = {start};
for (int i = 1; i < comp; i++) {
    if (d[i] > d[start]) {
        check.clear();
        check.pb(i);
        start = i;
    } else if (d[i] == d[start]) {
        check.pb(i);
    }
}
d.assign(comp, INF);
for (auto k: check) {
    if (d[k] == INF) {
        d[k] = 0;
        bfs(k);
    }
}
int dd = 0;
for (int i = 0; i < comp; i++) {
    if (d[i] != INF && d[i] > dd) dd = d[i];
}