#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e3 + 25;
int col[MAXN];
vector <int> adj[MAXN];
int n, m;
void dfs (int pos, int c) {
if (col[pos] != -1) {
if (col[pos] != c) {
cout << "NO\n";
exit(0);
}
return;
}
col[pos] = c;
for (auto j : adj[pos]) {
dfs(j, c ^ 1);
}
}
int main () {
cin >> n >> m;
for (int i = 1; i <= m; i++) {
int a, b;
cin >> a >> b;
adj[a].push_back(b);
adj[b].push_back(a);
}
memset(col, -1, sizeof(col));
dfs(1, 0);
cout << "YES\n";
if (n == 1) {
cout << "1\n1\n";
return 0;
}
if (n == 2) {
cout << "2\n2 2\n";
return 0;
}
cout << 2 * (n - 2) << '\n';
for (int i = 2; i < n; i++) cout << i << " ";
for (int i = n - 1; i >= 2; i--) cout << i << " ";
cout << '\n';
}
