#include <iostream>
#include <vector>
using namespace std;
vector<int> adj[100001];
int main()
{
    int jok[10001];
    int n, m,a,b,db=0;
    cin >> n >> m;
    for (int i = 1; i <= m; i++) {
        cin >> a >> b;
        adj[b].push_back(a);
        adj[a].push_back(b);
    }
    for (int i = 1; i <= n; i++) {
        if (adj[i].size() == 1) {
            int elozo = i;
            int most=adj[i][0];
            db++;
            jok[db] = most;
            while (adj[most].size() == 2) {
               
                if (adj[most][0] != elozo) {
                    elozo = most;
                    most = adj[elozo][0];
                    db++;
                    jok[db] = most;
                }
                else {
                    elozo = most;
                    most = adj[elozo][1];
                    db++;
                    jok[db] = most;
                }
            }
        }
    }
    cout << db << endl;
    for (int i = 1; i <= db; i++) {
        cout << jok[i]<<" ";
    }
}