#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>#define INF 100000000using namespace std;const int NN=150;const int MM=20000;const double eps=1e-6;int n,m,S,T,NV,en,head[NN],a[MM],b[MM],d[NN];struct Edge{ int u,v,next; double flow;} e[MM];void add(int u,int v,double flow){ e[en].u=u; e[en].v=v; e[en].flow=flow; e[en].next=head[u]; head[u]=en++; e[en].u=v; e[en].v=u; e[en].flow=0; e[en].next=head[v]; head[v]=en++;}void build(double g){ en=0; memset(head,-1,sizeof(head)); S=0; T=n+1; NV=T+1; for (int i=1; i<=n; i++) { add(S,i,m); add(i,T,m+g*2-d[i]); } for (int i=1; i<=m; i++) { add(a[i],b[i],1); add(b[i],a[i],1); }}int cur[NN],gap[NN],dis[NN],pre[NN];double sap(){ double maxflow=0; for(int i=0; i<NV; i++) { dis[i]=gap[i]=0; cur[i]=head[i]; } int u=pre[S]=S; double aug=INF; gap[0]=NV; while(dis[S]<NV) {loop: for(int &i=cur[u]; i!=-1; i=e[i].next) { int v=e[i].v; if(e[i].flow>0 && dis[u]==dis[v]+1) { if (e[i].flow<aug) aug=e[i].flow; pre[v]=u; u=v; if(v==T) { maxflow+=aug; for(u=pre[u]; v!=S; v=u,u=pre[u]) { e[cur[u]].flow-=aug; e[cur[u]^1].flow+=aug; } aug=INF; } goto loop; } } int min_dis=NV; for(int i=head[u]; i!=-1; i=e[i].next) { int v=e[i].v; if(e[i].flow>0 && min_dis>dis[v]) { cur[u]=i; min_dis=dis[v]; } } if(--gap[dis[u]]==0) break; gap[dis[u]=min_dis+1]++; u=pre[u]; } return maxflow;}void bisearch(){ double eps2=1.0/n/n; double mid,l=0,r=m; while (r-l>=eps2) { mid=(l+r)*0.5; build(mid); double h=((double)m*n-sap())*0.5; if (h>=eps) l=mid; else r=mid; } build(l); sap();}bool mark[NN];int tot,ans[NN];void dfs(int u){ mark[u]=true; if (u>=1 && u<=n) ans[tot++]=u; for (int i=head[u]; i!=-1; i=e[i].next) { int v=e[i].v; if (e[i].flow>0 && !mark[v]) dfs(v); }}void output(){ tot=0; memset(mark,false,sizeof(mark)); dfs(S); sort(ans,ans+tot); printf("%dn",tot); for (int i=0; i<tot; i++) printf("%dn",ans[i]);}int main(){ while (scanf("%d%d",&n,&m)!=EOF) { if (m==0) { printf("1n1n"); continue; } memset(d,0,sizeof(d)); for (int i=1; i<=m; i++) { scanf("%d%d",&a[i],&b[i]); d[a[i]]++; d[b[i]]++; } bisearch(); output(); } return 0;}
