#define here cerr<<"===========================================\n"
#define dbg(x) cerr<<#x<<": "<<x<<endl;
#include <bits/stdc++.h>
#define ld double
#define ll long long
#define ull unsigned long long
#define llinf 100000000000000000LL // 10^17
#define iinf 2000000000 // 2*10^9
#define pb push_back
#define eb emplace_back
#define popb pop_back
#define fi first
#define sc second
#define endl '\n'
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pld pair<ld,ld>
#define all(a) a.begin(),a.end()
#define ceri(a,l,r) {cerr<<#a<<": ";for(ll i_ = l;i_<=r;i_++) cerr<<a[i_]<< " ";cerr<<endl;}
#define cer(a) {cerr<<#a<<": ";for(ll x_ : a) cerr<<x_<< " ";cerr<<endl;}
#define si(a) (ll)(a.size())
using namespace std;
#define maxn 500005
ll n,m;
vector<ll> g[maxn];
set<ll> s;
void tc(){
cin >> n >> m;
for(ll i = 1;i<=m;i++){
ll x,y; cin >> x >> y;
g[x].pb(y);
g[y].pb(x);
}
for(ll i = 1;i<=n;i++) s.insert(i);
vector<ll> ans;
while(si(s)){
ll x = *s.begin();
s.erase(s.begin());
ans.pb(x);
for(ll x : g[x]){
if(s.find(x)!=s.end()) s.erase(s.find(x));
}
}
cout<<si(ans)<<endl;
for(ll x : ans) cout<<x<<" ";
cout<<endl;
}
int main(){
ios_base::sync_with_stdio(false);cerr.tie(0);cout.tie(0);cin.tie(0);
int t; t = 1;
while(t--){
tc();
}
return (0-0);
}
