int timer = 0, n, m;
vector<bool> used;
vector<int> tin, dp;
vector<vector<int>> g;
set<int> ans;

void dfs(int v, int p = -1) {
    used[v] = 1;
    tin[v] = dp[v] = timer++;
    int c = 0;
    for (auto to : g[v]) {
        if (to == p) continue;
        if (used[to]) {
            dp[v] = min(tin[to], dp[v]);
        } else {
            c++;
            dfs(to, v);
            dp[v] = min(dp[v], dp[to]);
            if (p != -1 && dp[to] >= tin[v]) {
                ans.insert(v);
            }
        }
    }
    if (p == -1 && c > 1) ans.insert(v);
}