#include <bits/stdc++.h> #define int long long #define sz(a) (int)a.size() #define all(a) a.begin(), a.end() #define rall(a) a.rbegin(), a.rend() using namespace std; vector<vector<int>> neigh; vector<int> lngst; vector<int> sz; vector<int> ans; int n; int mx; int mxI; int mxI2; bool np=false; pair<int,int> dfs(int x, int p){ int cmx1=0; int cmx2=0; int cmxI=x; int cmxI2=-1; for (auto u : neigh[x]) { if(u==p) continue; pair<int,int> df=dfs(u,x); if(df.first>cmx1){ cmx2=cmx1; cmxI2=cmxI; cmx1=df.first; cmxI=df.second; }else if(df.first>cmx2){ cmx2=df.first; cmxI2=x; } if(cmx1+cmx2>mx){ mx=cmx1+cmx2; mxI=cmxI; mxI2=cmxI2; } } return {cmx1+1,cmxI}; } void color(int x, int p){ for (auto u : neigh[x]) { if(u==p) continue; color(u,x); } if(x==mxI2) { lngst[x]=true; mxI2=p; } return; } int findsz(int x, int p){ sz[x]=1; for (auto u : neigh[x]) { if(u==p) continue; sz[x]+=findsz(u,x); } if(!lngst[x]&&sz[x]>2) np=true; return sz[x]; } void solve(int x, int p){ int nxt=-1; if(x!=mxI&&x!=mxI2) ans.push_back(x); for (auto u : neigh[x]) { if(u==p) continue; if(lngst[u]) nxt=u; else if(sz[u]==1) continue; else { ans.push_back(u); ans.push_back(x); } } if(nxt>=0) solve(nxt, x); return; } signed main() { ios_base::sync_with_stdio(false); cin.tie(nullptr); int m; cin >> n >> m; neigh.resize(n); sz.resize(n); lngst.resize(n); mx=0; mxI=0; for (int i = 0; i < m; i++) { int a,b; cin >> a >> b; a--; b--; neigh[a].push_back(b); neigh[b].push_back(a); } if(m>=n) { cout<< "NO\n"; return 0; } dfs(0,-1); int root=mxI; color(root,-1); findsz(root,-1); if(np){ cout << "NO\n"; return 0; } solve(root,-1); cout << "YES\n"; cout << sz(ans)*2 << "\n"; for (int i = 0; i < sz(ans); i++) cout << ans[i]+1 << " "; for (int i = 0; i < sz(ans); i++) cout << ans[sz(ans)-i-1]+1 << " "; return 0; }