#include <bits/stdc++.h>
using namespace std;
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int n, m;
cin >> n >> m;
vector<vector<int>> g(n);
for (int i = 0; i < m; i++) {
int u, v;
cin >> u >> v;
--u; --v;
g[u].push_back(v);
g[v].push_back(u);
}
vector<int> col(n, -1);
function<void(int)> Dfs = [&](int v) {
for (int u : g[v]) {
if (col[u] == -1) {
col[u] = col[v] ^ 1;
Dfs(u);
} else {
if (col[u] == col[v]) {
cout << "NO" << '\n';
exit(0);
}
}
}
};
for (int i = 0; i < n; i++) {
if (col[i] == -1) {
col[i] = 0;
Dfs(i);
}
}
cout << "YES" << '\n';
if (n == 1) {
cout << 1 << '\n' << 1 << '\n';
}
if (n == 2) {
cout << 2 << '\n' << 2 << " " << 2 << '\n';
}
if (n >= 3) {
cout << 2 * (n - 2) << '\n';
for (int i = 2; i < n; i++) {
cout << i << " " << i << " ";
}
}
return 0;
}
