#include<bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define pb push_back
#define inf 0x3f3f3f3f
using namespace std;
const int N=505;
int T,n,m,cnt,used[N],to[N],bl[N],fa[N],sb;
int low[N],dfn[N],num,fk[N],vs[N];
stack<int>stk;
vector<int>G[N];
vector<int>G0[N]; 
pair<int,int>a[N*N];
pair<int,int>p[N];
mt19937 gen(time(0));
bool dfs(int u){
	used[u]=1;
	shuffle(G[u].begin(),G[u].end(),gen);
	for(auto v:G[u]){
		if(used[v])continue;
		used[v]=1;
		int x=to[v];
		to[u]=v,to[v]=u,to[x]=0;
		if(!x||dfs(x))return 1;
		to[v]=x,to[x]=v,to[u]=0;
	}
	return 0;
}
void init(){
	for(int i=1;i<=2*cnt;i++)fa[i]=i,dfn[i]=low[i]=fk[i]=vs[i]=0,G0[i].clear();num=sb=0;
}
void add(int x,int y){
	G0[x].pb(y);
}
void work(int u,int v){
	if(!bl[u]){
		if(v==p[bl[v]].fi)add(bl[v]+cnt,bl[v]);
		else add(bl[v],bl[v]+cnt);
	}
	else if(!bl[v]){
		if(u==p[bl[u]].fi)add(bl[u]+cnt,bl[u]);
		else add(bl[u],bl[u]+cnt);
	}
	else{
		int x=(u==p[bl[u]].se),y=(v==p[bl[v]].se);
		add(bl[u]+(1-x)*cnt,bl[v]+y*cnt);
		add(bl[v]+(1-y)*cnt,bl[u]+x*cnt); 
	}
}
void tarjan(int u){
	low[u]=dfn[u]=++num,stk.push(u),vs[u]=1;
	for(auto v:G0[u]){
		if(!dfn[v]){
			tarjan(v);
			low[u]=min(low[u],low[v]);
		}
		else if(vs[v]){
			low[u]=min(low[u],dfn[v]);
		}
	}
	if(low[u]==dfn[u]){
		int tmp=0;sb++;
		do{
			tmp=stk.top(),stk.pop();
			fk[tmp]=sb,vs[tmp]=0;
		}while(tmp!=u);
	}
}
int main(){
	//freopen("data.in","r",stdin);
	ios::sync_with_stdio(false);
	cin.tie(0),cout.tie(0);
//	cin>>T;
//	while(T--){
		cin>>n>>m;for(int i=1;i<=n;i++)G[i].clear(),bl[i]=to[i]=0;
		for(int i=1;i<=m;i++){
			int u,v;cin>>u>>v;
			G[u].pb(v),G[v].pb(u);
			if(!to[u]&&!to[v])to[u]=v,to[v]=u;
			//cout<<"edge:"<<u<<" "<<v<<"\n";
			a[i]={u,v};
		}
		for(int k=1;k<=1000;k++){
			for(int i=1;i<=n;i++){
				if(!to[i]){
					for(int j=1;j<=n;j++)used[j]=0;
					dfs(i);
				}
			}
		}
		cnt=0;
		for(int i=1;i<=n;i++){
			if(to[i]&&i<to[i]){
				p[++cnt]={i,to[i]};
				bl[i]=bl[to[i]]=cnt;
			}
		}
//		cout<<cnt<<"\n";
//		 for(int i=1;i<=cnt;i++){
//		 	cout<<p[i].fi<<" "<<p[i].se<<"\n";
//		 }
		init();
		for(int i=1;i<=m;i++){
			int u=a[i].fi,v=a[i].se;
			if(bl[u]==bl[v])continue;
			work(u,v);
		}
		for(int i=1;i<=cnt*2;i++)if(!dfn[i])tarjan(i);
		bool ok=1;
		for(int i=1;i<=cnt;i++)if(fk[i]==fk[i+cnt])ok=0;
		if(ok){
			cout<<cnt<<"\n";
			for(int i=1;i<=cnt;i++){
				if(fk[i]<fk[i+cnt])cout<<p[i].fi<<" ";
				else cout<<p[i].se<<" ";
			}
			cout<<"\n";
		}
		else{
			bool flg=0;
			for(int i=1;i<=n;i++){
				init();
				if(to[i]){
					for(int j=1;j<=m;j++){
						int u=a[j].fi,v=a[j].se;
						if(bl[u]==i||bl[v]==i||bl[u]==bl[v])continue;
						work(u,v);
					}
					for(int j=1;j<=cnt*2;j++)if(!dfn[j])tarjan(j);
					bool ok=1;
					for(int j=1;j<=cnt;j++)if(fk[j]==fk[j+cnt])ok=0;
					if(ok){
						flg=1;
						cout<<cnt+1<<"\n";
						for(int j=1;j<=cnt;j++){
							if(j==i)cout<<p[j].fi<<" "<<p[j].se<<" ";
							else if(fk[j]<fk[j+cnt])cout<<p[j].fi<<" ";
							else cout<<p[j].se<<" ";
						}
						cout<<"\n";
						break;
					}
				}
				else{
					for(int j=1;j<=m;j++){
						int u=a[j].fi,v=a[j].se;
						if(u==i||v==i||bl[u]==bl[v])continue;
						work(u,v);
					}
					for(int j=1;j<=cnt*2;j++)if(!dfn[j])tarjan(j);
					bool ok=1;
					for(int j=1;j<=cnt;j++)if(fk[j]==fk[j+cnt])ok=0;
					if(ok){
						flg=1;
						cout<<cnt+1<<"\n";
						cout<<i<<" ";
						for(int j=1;j<=cnt;j++){
							if(fk[j]<fk[j+cnt])cout<<p[j].fi<<" ";
							else cout<<p[j].se<<" ";
						}
						cout<<"\n";
						break;
					}
				}
			}
			if(!flg)cout<<"not smol"<<"\n";
		}
//	}
}