#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;
#define speed cin.tie(nullptr); cout.tie(nullptr); ios::sync_with_stdio(0)

vector<vector<int>> neighborS;
vector<bool> visited;
vector<int> result;

void dfs(int node) {
    if (visited[node]) return;
    visited[node] = 1;

    result.push_back(node);

    if (neighborS[node].size() <= 2) {
        for (int neighbor : neighborS[node]) {
            dfs(neighbor);
        }
    }
}

int main() {
    speed;

    int N, M;
    cin >> N >> M;

    neighborS.resize(N + 1);
    visited.resize(N + 1);
    
    while (M--) {
        int U, V;
        cin >> U >> V;
        neighborS[U].push_back(V);
        neighborS[V].push_back(U);
    }

    for (int i = 1; i <= N; i++) {
        if (neighborS[i].size() == 1) { // zsakfalu
            visited[i] = 1;
            dfs(neighborS[i][0]);
        }
    }
    
    if (result.empty()) {
        cout << 0;
        exit(0);
    }

    sort(result.begin(), result.end());

    cout << result.size() << '\n';
    for (int i = 0; i < result.size(); i++) {
        cout << result[i] << ' ';
    }
}