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

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

void DFS(int u){
    seen[u]=1;
    if (graf[u].size()<3){
        for(int v:graf[u]){
            if (seen[v]==0){ans.push_back(v+1);DFS(v);}
        }
    }
    return;
}

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