#include <bits/stdc++.h>

using namespace std;

int n, m;
vector<int> a;
vector<int> b;
vector<int> utak;
vector<int> o (0);

void bejar(int c, int d)
{
    for (int i = 0; i < m; i++)
    {
        if (a[i] == c && b[i] != d)
        {
            o.push_back(b[i]);
            if (utak[b[i]] <= 2)
            {
                bejar(b[i], c);
            }
        }
        if (b[i] == c && a[i] != d)
        {
            o.push_back(a[i]);
            if (utak[a[i]] <= 2)
            {
                bejar(a[i], c);
            }
        }
    }
}

int main()
{
    cin >> n >> m;
    a.resize(m);
    b.resize(m);
    utak.resize(n +1, 0);
    for (int i = 0; i < m; i++)
    {
        cin >> a[i] >> b[i];
        utak[a[i]]++;
        utak[b[i]]++;
    }
    for (int i = 1; i <= n; i++)
    {
        if (utak[i] == 1)
        {
            bejar(i, -1);
        }
    }
    cout << o.size() << endl;
    for (int i = 0; i < o.size(); i++)
    {
        cout << o[i] << " ";
    }
    return 0;
}