#include <bits/stdc++.h>
using namespace std;
#define fs first
#define sc second
#define mp make_pair
#define FOR(i, j, k) for (int i = j, Z = k; i < Z; i++)
using ll = long long;
typedef pair<int, int> pii;
const int MXN = 500005;
int n, m;
vector<int> edge[MXN];
bool ban[MXN];
vector<int> ans;
void solve() {
int x, y;
cin >> n >> m;
while (m--) {
cin >> x >> y;
edge[x].push_back(y);
edge[y].push_back(x);
}
FOR(id, 1, n + 1) {
if (ban[id]) continue;
ans.push_back(id);
for (auto &i : edge[id]) ban[i] = true;
}
cout << ans.size() << '\n';
for (auto &i : ans) cout << i << ' ';
cout << '\n';
}
int32_t main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
solve();
return 0;
}
