//Achen
#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdlib>
#include<vector>
#include<cstdio>
#include<queue>
#include<cmath>
const int N=12007;
typedef double LL;
const LL inf=1e18,eps=1e-12;
using namespace std;
int n,m,num;template<typename T>void read(T &x)  {char ch=getchar(); x=0; T f=1;while(ch!='-'&&(ch<'0'||ch>'9')) ch=getchar();if(ch=='-') f=-1,ch=getchar();for(;ch>='0'&&ch<='9';ch=getchar()) x=x*10+ch-'0'; x*=f;
}struct edge{int from,to,nx;LL cap,flow;edge(){}edge(int from,int to,LL cap,LL flow,int nx):from(from),to(to),cap(cap),flow(flow),nx(nx){}
}e[N];int ecnt=1,fir[N],dd[N];
void add(int u,int v,LL cap) {e[++ecnt]=edge(u,v,cap,0,fir[u]); fir[u]=ecnt;e[++ecnt]=edge(v,u,0,0,fir[v]); fir[v]=ecnt;
}queue<int>que;
int c[N],d[N],cur[N],p[N];
void bfs(int s,int t) {for(int i=0;i<=num;i++) d[i]=num,c[i]=0;que.push(t); d[t]=0;while(!que.empty()) {int x=que.front();que.pop();for(int i=fir[x];i;i=e[i].nx) {int y=e[i].to;if(d[y]==num&&e[i].cap==0) {d[y]=d[x]+1;que.push(y);}}}
}LL cal(int s,int t) {LL fl=inf;for(int i=t;i!=s;i=e[p[i]].from)fl=min(fl,e[p[i]].cap-e[p[i]].flow);for(int i=t;i!=s;i=e[p[i]].from) {if(p[i]==886||((p[i]^1)==886)) {int debug=1;}e[p[i]].flow=e[p[i]].flow+fl,e[p[i]^1].flow-=fl;}return fl;
}LL ISAP(int s,int t) {bfs(s,t);LL res=0;for(int i=1;i<=num;i++) c[d[i]]++,cur[i]=fir[i];for(int x=s;d[x]<num;) {if(x==t) {res+=cal(s,t);x=s;} int ok=0;for(int &i=cur[x];i;i=e[i].nx) if(e[i].flow+eps<=e[i].cap&&d[e[i].to]+1==d[x]) {ok=1; p[x=e[i].to]=i; break;}if(!ok) {cur[x]=fir[x]; int M=num;for(int i=fir[x];i;i=e[i].nx) if(e[i].flow+eps<=e[i].cap) M=min(M,d[e[i].to]+1);if(!(--c[d[x]])) break;c[d[x]=M]++;if(x!=s) x=e[p[x]].from;}}return res;
}int vis[N],ansnum;
void dfs(int x) {for(int i=fir[x];i;i=e[i].nx) if(!vis[e[i].to]&&e[i].cap-e[i].flow>=eps) { vis[e[i].to]=1;ansnum++;dfs(e[i].to);}
}int ee[N][2];int ck(LL mid,int o) {int s=n+1,t=n+2,res=0; num=t;ecnt=1;memset(fir,0,sizeof(fir));    for(int i=1;i<=m;i++) {add(ee[i][0],ee[i][1],1);add(ee[i][1],ee[i][0],1);}for(int i=1;i<=n;i++) {add(s,i,(LL)m);add(i,t,(LL)m+2.0*mid-dd[i]);}if(((LL)n*m-ISAP(s,t))/2.0>=eps) res=1;if(o==1) {memset(vis,0,sizeof(vis));  vis[s]=1; dfs(s);}return res;
}int main() {while(scanf("%d%d",&n,&m)==2) {if( m == 0 ) {  printf("1\n1\n") ;  continue ;  }memset(dd,0,sizeof(dd));for(int i=1;i<=m;i++) {read(ee[i][0]); read(ee[i][1]);dd[ee[i][0]]++; dd[ee[i][1]]++;}LL l=0,r=m;while(l+1e-5<=r) {LL mid=(l+r)/2.0;if(ck(mid,0)) l=mid;else r=mid;}ansnum=0;ck(l,1); printf("%d\n",ansnum);for(int i=1;i<=n;i++) if(vis[i]) printf("%d\n",i);}return 0;
}