#include <iostream>
#include <set>
#include <vector>
using namespace std;

void bejar(int x, set <int> &megold, vector <int> fokszam, int n, vector <int> a, vector <bool> volt)
{
    int i, y;
    bool felt = true;
    volt[x] = true;
    for (i=0; i<n; i++)
    {
        if (a[x*n+i] == 1)
        {
            megold.insert(i+1);
            volt[i] = 1;
            y=i;
            do
            {
                if (fokszam[y]!=2)
                    break;
                felt=false;
                for (int j=0; j<n; j++)
                {
                    if (a[y*n+j]==1 && !volt[j])
                    {
                        megold.insert(j+1);
                        volt[j] = true;
                        y = j;
                        felt=true;
                        break;
                    }
                }
            }
            while (felt);
        }
    }
}

int main()
{
    vector <int> a;
    int  n, m, ossz;
    cin >> n >> m;
    a.resize(n*n);
    int x, y;
    for(int i = 0; i < m; i ++)
    {
        cin >> x >> y;
        x--;
        y--;
        a[x*n+y] = 1;
        a[y*n+x] = 1;
    }
    vector <int> fokszam;
    for(int i = 0 ; i < n; i ++)
    {
        ossz=0;
        for(int j =  0; j < n; j ++)
        {
            ossz+= a[i*n+j];
        }
        fokszam.push_back(ossz);
    }
    vector <bool> volt;
    volt.resize(n);
    set <int> halmaz;
    for(int i = 0; i < n; i ++)
    {
        if(fokszam[i] == 1)
        {
            bejar(i, halmaz, fokszam,n,a,volt);
        }
    }
    cout << halmaz.size() << endl;
    for(auto i : halmaz)
        cout << i << " ";
    return 0;
}