/**
* author: BERNARD B.01
**/
#include <bits/stdc++.h>
using namespace std;
#ifdef B01
#include "deb.h"
#else
#define deb(...)
#endif
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int n, m;
cin >> n >> m;
if (m != n - 1) {
cout << "NO" << '\n';
return 0;
}
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);
}
cout << "YES" << '\n';
if (n == 1) {
cout << 1 << '\n';
cout << 1 << '\n';
return 0;
}
if (n == 2) {
cout << 2 << '\n';
cout << 1 << '\n';
cout << 1 << '\n';
return 0;
}
vector<int> z;
for (int i = 2; i < n - 1; i++) {
z.push_back(i);
z.push_back(i);
if (i > 2) {
z.push_back(i - 1);
z.push_back(i);
}
}
cout << "YES" << '\n';
cout << (int) z.size() << '\n';
for (int i = 0; i < (int) z.size(); i++) {
if (i > 0) {
cout << " ";
}
cout << z[i];
}
cout << '\n';
return 0;
}
