#include <iostream>
#include <vector>


using namespace std;

void search_graph(int start, vector<vector<int>> &adj, bool visited[])
{
    int currNode = start;
    while(!visited[currNode]){
        visited[currNode] = true;
        if(adj[currNode].size() > 2){
            return;
        }
        for(int i = 0; i < adj[currNode].size(); i++){
            int newNode = adj[currNode][i];
            if(!visited[newNode]){
                currNode = newNode;
                break;
            }
        }
    }
}

int main()
{
    int N, M;
    vector<vector<int>> adj(N+1, vector<int>());
    cin >> N >> M;
    for(int i = 0; i < M; i++){
        int a, b;
        cin >> a >> b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    bool visited[10001] = {};
    for(int i = 1; i <= N; i++){
        if(adj[i].size() == 1){
            search_graph(i, adj, visited);
        }
    }

    vector<int> sol;
    for(int i = 1; i <= N; i++){
        if(visited[i] && adj[i].size() != 1){
            sol.push_back(i);
        }
    }
    cout << sol.size() << endl;
    for(int i = 0; i < sol.size(); i++){
        cout << sol[i] << " ";
    }
    cout << endl;

    return 0;
}