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

int n, m;

int main()
{
    cin >> n >> m;
    vector<int> visited(n + 1, false);
    vector<vector<int>> graph(n + 1, vector<int>());

    for (int i=0; i < m; i++) {
        int u, v;
        cin >> u >> v;
        graph[u].push_back(v);
        graph[v].push_back(u);
    }

    queue<int> q;
    vector<int> ans;
    for (int i=1; i <= n; i++) {
        if (graph[i].size() < 2) {
            q.push(i);
            visited[i] = true;
        }
    }

    while (!q.empty()) {
        int node = q.front();
        q.pop();

        if (graph[node].size() > 1) {
            ans.push_back(node);
        }

        if (graph[node].size() < 3) {
            for (int next : graph[node]) {
                if (!visited[next]) {
                    visited[next] = true;
                    q.push(next);
                }
            }
        }
    }

    sort(ans.begin(), ans.end());
    cout << ans.size() << '\n';
    for (int x : ans) cout << x << ' ';

    return 0;
}