// Elagazas nelkul.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#include <iostream>
#include <vector>
#include <queue>
int N, M, db = 0;
std::vector <int> fok(10001);
std::vector <int> helyes(10001);
std::vector <std::vector<int>> szomszed(10001);
void BFS(int k) {
    std::vector <int> cimke(N+1,-1);
    std::queue <int> sor;
    sor.push(k);
    cimke[k] = 0;
    int akt = 0;
    while (!sor.empty()) {
        int elem = sor.front();
        if (fok[elem] == 2 || fok[elem] == 1)
        for (auto e : szomszed[elem]) {
            
            if (cimke[e] == -1) {
                
                cimke[e] = akt + 1;

                
                    sor.push(e);
                    helyes[e] = 1;
                   // db++;
                 
                
            }
        }
        sor.pop();
        akt++;
    }
 }

int main()
{
    
    
    std::cin>> N >> M;
    
    int n = N+1;
    
    for (int i = 1; i <= M; i++) {
        int a, b;
        std::cin >> a >> b;
        szomszed[a].push_back(b);
        szomszed[b].push_back(a);
        fok[a]++;
        fok[b]++;
    }
    for (int i = 1; i <= N; i++) {
        //std::cout << fok[i] << " ";
        if (fok[i] == 1) {
            
           // std::cout <<"\n" << i << "Bejaras:";
            BFS(i);
        }
    }

    for (int i = 1; i <= N; i++) if (helyes[i] == 1) db++;
    std::cout  << db << std::endl;
    for(int  i = 1; i <= N; i++) if(helyes[i] == 1) std::cout << i << " ";
}