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

using namespace std;
int n;

vector<vector<int>> g;
vector<bool> used;
vector<int> comp;

void dfs(int v) {
    used[v] = true;
    comp.push_back(v);
    for (auto i = g[v].begin(); i != g[v].end(); ++i)
        if (!used[*i])
            dfs(*i);
}
int main() {
    int m, a, b, l;
    cin >> n >> m;
    g.resize(n);
    used.assign(n, false);
    for (int i = 0; i < m; i++) {
        cin >> a >> b;
        a--;
        b--;
        g[a].push_back(b);
        g[b].push_back(a);
    }
    dfs(0);
    cout << comp.size() << endl;
    sort(comp.begin(), comp.end());
    for (int i = 0; i < comp.size(); ++i) {
        cout << comp[i] + 1 << " ";
    }
    return 0;
}