#include <bits/stdc++.h>

using namespace std;

int main()
{
    ifstream cin("f.txt");
    int n, m, x, y, z;
    cin>>n>>m;
    vector<vector<int>> v1(n+1);
    bool volt[n+1]={};
    for(int i=1; i<=m; i++)
    {
        cin>>x>>y;
        v1[x].push_back(y);
        v1[y].push_back(x);
    }
    vector<int> vegfalu;
    queue<int> q;
    for(int i=1; i<=n; i++)
    {
        if(v1[i].size()==1)
        {
            vegfalu.push_back(i);
            q.push(i);
            volt[i]=true;
            //cout<<i<<" ";
        }
    }
    vector<int> megoldas;
    while(!q.empty())
    {
        z=q.front();
        q.pop();
        for(auto j:v1[z])
        {
            if(volt[j]==false and v1[j].size()==2)
            {
                megoldas.push_back(j);
                volt[j]=true;
                q.push(j);
            }
            if(!volt[j]){
                megoldas.push_back(j);
                volt[j]=true;
            }
        }
    }
    cout<<megoldas.size()<<endl;
    sort(megoldas.begin(), megoldas.end());
    for(int i=0; i<megoldas.size(); i++)
    {
        cout<<megoldas[i]<<" ";
    }
    return 0;
}