#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <set>
#include <unordered_set>
#include <string>

class Graph {
 private:
    std::map<int, std::unordered_set<int>> edges;
    std::set<int> used;

 public:
    Graph() {
    }

    void insert(int a, int b) {
        edges[a].insert(b);
        edges[b].insert(a);
    }

    void subgraph2(int a) {
        if (used.find(a) == used.end()) {
            used.insert(a);
            for (auto i : edges[a]) {
                subgraph2(i);
            }
        }
    }

    std::set<int> subgraph(int a) {
        used.clear();
        subgraph2(a);
        return used;
    }
};

int main() {
    int N, M;
    int a, b;
    std::cin >> N >> M;
    if (M != 0) {
        Graph graph;
        for (int i = 0; i < M; i++) {
            std::cin >> a >> b;
            graph.insert(a, b);
        }
        std::set<int> result = graph.subgraph(1);
        auto b = result.begin();
        std::cout << result.size() << '\n';
        std::cout << *b++;
        while (b != result.end()) {
            std::cout << " " << *b++;
        }
    } else {
        std::cout << 1 << '\n' << 1;
    }
}