#include<bits/stdc++.h>
#define rep(i,j,k) for(int i=j;i<=k;i++)
using namespace std;
const int N=505;
int T,n,m,bh,bh1,fans,dans[N],u[N*N],vv[N*N],dy[N],vis[N];
vector<int> v[N];
mt19937 rd(time(0));
bool dfs(int x){
	if(vis[x]) return 0; vis[x]=1;
	for(auto dq:v[x]) if(!vis[dq]&&(!dy[dq]||dfs(dy[dq]))){dy[dq]=x,dy[x]=dq; return 1;}
	return 0;
}
struct ts{
	int ds,idx,ys,dfn[2*N],low[2*N],col[2*N],vis[2*N];
	vector<int> e[2*N];
	stack<int> st;
	void ade(int x,int y){e[x].push_back(y);}
	void cl(){rep(i,1,ds) e[i].clear();}
	void tj(int x){
		dfn[x]=low[x]=++idx,vis[x]=1,st.push(x);
		for(auto dq:e[x]){
			if(!dfn[dq]) tj(dq),low[x]=min(low[x],low[dq]);
			else if(vis[dq]) low[x]=min(low[x],dfn[dq]);
		}
		if(low[x]==dfn[x]){
			ys++;
			while(1){
				int dq=st.top(); vis[dq]=0,st.pop();
				col[dq]=ys; if(dq==x) break;
			}
		}
	}
	bool cz(){
		idx=ys=0;
		rep(i,1,ds) dfn[i]=low[i]=col[i]=0;
		rep(i,1,ds) if(!dfn[i]) tj(i);
		rep(i,1,n) if(col[i]==col[i+n]) return 0;
		return 1;
	}
	void sc(){
		int ans=0; vector<int> av;
		rep(i,1,n) if(col[i+n]<col[i]) ans++,av.push_back(i);
		printf("%d\n",ans);
		for(auto dq:av) printf("%d ",dq);
		puts("");
	}
}G;
void jb(){
	rep(i,1,m) if(i!=bh){
		if(dy[u[i]]==vv[i]) G.ade(u[i],vv[i]+n),G.ade(vv[i]+n,u[i]),G.ade(vv[i],u[i]+n),G.ade(u[i]+n,vv[i]);
		else G.ade(u[i],vv[i]+n),G.ade(vv[i],u[i]+n);
	}
	rep(i,1,n) if(!dy[i]&&i!=bh1) G.ade(i+n,i);
}
void sol(){
	rep(i,1,n) v[i].clear();
	rep(i,1,m) scanf("%d",&u[i],&vv[i]),v[u[i]].push_back(vv[i]),v[vv[i]].push_back(u[i]);
	fans=0;
	rep(i,1,n) dans[i]=0;
	rep(T,1,10){
		int ans=0;
		rep(i,1,n) dy[i]=0,shuffle(v[i].begin(),v[i].end(),rd);
		rep(i,1,n) if(!dy[i]){rep(j,1,n) vis[j]=0; ans+=dfs(i);}
		if(ans>fans){fans=ans; rep(i,1,n) dans[i]=dy[i];}
	}
	rep(i,1,n) dy[i]=dans[i];
	G.ds=2*n,G.cl(),bh=0,jb();
	if(G.cz()){G.sc(); return ;}
	rep(i,1,m) if(dy[u[i]]==vv[i]){
		G.cl(),bh=i,G.ade(u[i],vv[i]+n),G.ade(vv[i],u[i]+n),jb();
		if(G.cz()){G.sc(); return ;}
	}bh=0;
	rep(i,1,n) if(!dy[i]){
		G.cl(),bh1=i,G.ade(i,i+n),jb();
		if(G.cz()){G.sc(); return ;}
	}puts("not smol");
}
signed main(){
	ios::sync_with_stdio(false);
	while(scanf("%d%d",&n,&m)!=-1) sol();
}