// Author : FatihCihan
#include <bits/stdc++.h>
using namespace std;
#define all(v) v.begin() , v.end()
#define sz(a) (int)a.size()
void solve(){
int n,m;
cin >> n >> m;
vector < int > graph[n];
for(int i = 0;i<m;i++){
int a,b;
cin >> a >> b;
a-- , b--;
graph[a].push_back(b);
graph[b].push_back(a);
}
int vis[n] = {0};
vector < int > ans;
for(int i = 0;i<n;i++){
if(vis[i] == 0){
ans.push_back(i+1);
for(auto itr : graph[i]){
vis[itr] = 1;
}
}
}
cout << sz(ans) << endl;
for(auto itr : ans){
cout << itr << " ";
}
cout << endl;
}
signed main(){
ios_base::sync_with_stdio(0);cin.tie(0);
int testcase = 1;//cin >> testcase;
while(testcase--)solve();
cerr << 1000.0 * clock() / CLOCKS_PER_SEC << " ms" << endl;
}
