/**
* 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;
}
cout << 2 * n - 4 << '\n';
for (int i = 1; i < n - 1; i++) {
cout << i + 1 << '\n';
}
for (int i = n - 2; i >= 1; i--) {
cout << i + 1 << '\n';
}
return 0;
}
