#include <algorithm>
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned long long
#define ld long double
#define ff first
#define ss second
#define ln "\n"
#define mp make_pair
#define pb push_back
#define INF (ll)1e18
ll MOD = (ll)(1e9+7);
void solve(){
ll n, m; cin >> n >> m;
if (n==1){
cout << "YES\n1\n1\n"; return;
}else if (n==2){
ll _; cin >> _ >> _;
cout << "YES\n2\n1 1\n"; return;
}
for (ll i=0; i<m; i++){
ll u, v; cin >> u >> v;
}
cout << "YES" << ln;
cout << (n-2)*2 << ln;
for (ll i=2; i<=n-1; i++){
cout << i << " " << i << " ";
}
cout << ln;
}
int main(){
ios_base::sync_with_stdio(false); cin.tie(nullptr);
#ifdef LOCAL
auto start = chrono::high_resolution_clock::now();
#endif
ll testc=1;
// cin >> testc;
for (ll __c=1; __c<=testc; __c++) solve();
#ifdef LOCAL
auto duration = chrono::duration_cast<chrono::microseconds>(chrono::high_resolution_clock::now() - start);
cout << setprecision(0) << fixed << "time: " << (double)duration.count()/1000.0 << " milliseconds" << endl;
#endif
}
