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

vector<int> ans;
vector<vector<int>> graf;
vector<bool> seen;

void DFS(int u) {
  if (seen[u]) return;
  seen[u] = 1;
  if (graf[u].size() >= 3) return;
  for (int v : graf[u]) DFS(v);
}

int main(){
    int n,m; cin >> n >> m;
    graf.resize(n);
    seen.resize(n,0);
    for (int i=0;i<m;i++){
        int u,v; cin >> u >> v;
        graf[u-1].push_back(v-1);
        graf[v-1].push_back(u-1);
    }
    for (int i=0;i<n;i++){
        if (graf[i].size()==1){
            DFS(i);
        }
    }
    for (int i = 0; i < n; i++) {
    if (seen[i] && graf[i].size() != 1) ans.push_back(i+1);
    }

    cout << ans.size() << "\n";
    for (int i:ans){cout << i << " ";}
}