#include <bits/stdc++.h>
using namespace std;
void dfs(int x, vector<vector<int>> &AR, vector<int> &color, int c)
{
if (color[x])
return;
color[x] = c;
for (int i = 0; i < AR[x].size(); i++)
dfs(AR[x][i], AR, color, 3 - c);
}
int main()
{
int N, M;
cin >> N >> M;
vector<vector<int>> AR(N);
for (int i = 0; i < M; i++)
{
int a, b;
cin >> a >> b;
a--, b--;
AR[a].push_back(b);
AR[b].push_back(a);
}
vector<int> color(N);
int tot = 0;
for (int i = 0; i < N; i++)
{
dfs(i, AR, color, 1);
if (color[i] == 1)
tot++;
}
cout << tot << '\n';
for (int i = 0; i < N; i++)
if (color[i] == 1)
cout << i + 1 << ' ';
}
