#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N=100005;
const int inf=1e18;
int n,m,u[N],v[N],head[N<<4],cnt=1;
double eps=1e-8;
struct node{int to,nxt;double w;}e[N<<4];
void add(int u,int v,double w){
	e[++cnt].to=v;
	e[cnt].w=w;
	e[cnt].nxt=head[u];
	head[u]=cnt;
}
int s,t,now[N],deep[N];
bool bfs(){
	for(int i=1;i<=t;i++)deep[i]=inf;
	deep[s]=0;
	now[s]=head[s];
	queue<int> q;
	q.push(s);
	while(!q.empty()){
		int u=q.front();
		q.pop();
		for(int i=head[u];i;i=e[i].nxt){
			int v=e[i].to;
			if(e[i].w&&deep[v]==inf){
				q.push(v);
				deep[v]=deep[u]+1;
				now[v]=head[v];
				if(v==t)return 1;
			}
		}
	}
	return 0;
}
double dfs(int u,double sum){
	if(u==t)return sum;
	double k,flow=0;
	for(int i=head[u];i&&sum;i=e[i].nxt){
		int v=e[i].to;
		if(e[i].w&&(deep[v]==deep[u]+1)){
			k=dfs(v,min(e[i].w,sum));
			if(!k)deep[v]=inf;
			e[i].w-=k;
			e[i^1].w+=k;
			flow+=k;
			sum-=k;
		}
	}
	return flow;
}
double op;
bool check(double x){
	cnt=1;
	s=m+n+1,t=s+1;
    for(int i=1;i<=t;i++)head[i]=0;
	for(int i=1;i<=m;i++){
		add(s,i+n,1);
		add(i+n,s,0);
		add(i+n,u[i],inf);
		add(u[i],i+n,0);
		add(i+n,v[i],inf);
		add(v[i],i+n,0);
	}
	for(int i=1;i<=n;i++){
		add(i,t,x);
		add(t,i,0);
	}
    op=0;
	while(bfs()){
		op+=dfs(s,inf);
	}
   // cout<<op<<endl;
	return m-op>0;
}
int tot;
bool vis[N];
void dfs1(int x){
	vis[x]=1;
	for(int i=head[x];i;i=e[i].nxt){
		int v=e[i].to;
		double w=e[i].w;
		if(!vis[v]&&w)dfs1(v);
	}
}
vector<int> o;
signed main(){
	while(cin>>n>>m){
        memset(vis,0,sizeof(vis));
        if(m==0){cout<<1<<endl<<1<<endl;continue;}
		for(int i=1;i<=m;i++){
			cin>>u[i]>>v[i];
		}
		double l=0,r=2e9,ans=-1;
		while(l+eps<r){
			double mid=(l+r)/2;
			//cout<<mid<<endl;
			if(check(mid))ans=mid,l=mid;
			else r=mid;
		}
		check(ans);
		dfs1(s);
        tot=0;
        o.clear();
		for(int i=1;i<=n;i++){
			if(vis[i]){
				o.push_back(i);
				tot++;
			}
		}
		cout<<tot<<endl;
		for(int i:o)cout<<i<<endl;
        cout<<endl;
	}
	return 0;
}