#include <cstdio>

#include <cstring>

#include <iostream>

#include <cmath>

#include <algorithm>

#include <vector>

#include <string>

#include <set>

#include <queue>

using namespace std;

#define ll long long

#define MP make_pair

#define mxn 110

#define mxe 4500

#define inf 1e9

#define eps 1e-8

vector<int>ans;

struct SAP{

	int dis[mxn],pre[mxn],gap[mxn],arc[mxn];

	double f[mxe],cap[mxe];

	int head[mxn],nxt[mxe],vv[mxe],e;

	void init(){e=0;memset(head,-1,sizeof(head));}

	void add(int u,int v,double c){

		vv[e]=v,cap[e]=c,nxt[e]=head[u],head[u]=e++;

		vv[e]=u,cap[e]=0,nxt[e]=head[v],head[v]=e++;

	}

	void bfs(int s){

		int q[mxn];

		int ht=0,tl=0;

		q[tl++]=s;

		ans.clear();

		bool vis[mxn];

		memset(vis,false,sizeof(vis));

		vis[s]=true;

		while(ht<tl){

			int u = q[ht++];

			for(int i=head[u];i!=-1;i=nxt[i]){

				int v = vv[i];

				if(!vis[v] && cap[i]-f[i]){

					vis[v]=true;

					q[tl++]=v;

					if(v<s) ans.push_back(v);

				}

			}

		}

	}

	double max_flow(int s,int t,int n){

		int q[mxn],j,mindis;

		double ans=0;

		int ht=0,tl=1,u,v;

		double low;

		bool found,vis[mxn];

		memset(dis,0,sizeof(dis));

		memset(gap,0,sizeof(gap));

		memset(vis,0,sizeof(vis));

		memset(arc,-1,sizeof(arc));

		memset(f,0,sizeof(f));

		q[0]=t;vis[t]=true;dis[t]=0;gap[0]=1;

		while(ht<tl){

			u=q[ht++];

			for(int i=head[u];i!=-1;i=nxt[i]){

				v = vv[i];

				if(!vis[v]){

					vis[v]=true;

					dis[v]=dis[u]+1;

					q[tl++]=v;

					gap[dis[v]]++;

					arc[v]=head[v];

				}

			}

		}

		u=s;low=inf;pre[s]=s;

		while(dis[s]<n){

			found=false;

			for(int &i=arc[u];i!=-1;i=nxt[i]){

				if(dis[vv[i]]==dis[u]-1 && cap[i]>f[i]){

					found=true;v=vv[i];

					low=min(low,cap[i]-f[i]);

					pre[v]=u;u=v;

					if(u==t){

						while(u!=s){

							u=pre[u];

							f[arc[u]]+=low;

							f[arc[u]^1]-=low;

						}

						ans+=low;low=inf;

					}

					break;

				}

			}

			if(found) continue;

			mindis=n;

			for(int i=head[u];i!=-1;i=nxt[i]){

				if(mindis>dis[vv[i]] && cap[i]>f[i]){

					mindis=dis[vv[j=i]];

					arc[u]=i;

				}

			}

			if(--gap[dis[u]]==0) return ans;

			dis[u]=mindis+1;

			gap[dis[u]]++;

			u=pre[u];

		}

		return ans;

	}

}sap;

int e[1010][2];

int deg[110];

int n,m;

bool jud(double g){

	sap.init();

	for(int i=0;i<m;++i){

		sap.add(e[i][0],e[i][1],1);

		sap.add(e[i][1],e[i][0],1);

	}

	for(int i=1;i<=n;++i) sap.add(n+1,i,m);

	for(int i=1;i<=n;++i) sap.add(i,n+2,m+2*g-deg[i]);

	double mf = sap.max_flow(n+1,n+2,n+2);

	return (n*m-mf)/2>eps;

}

int main(){

	while(~scanf("%d%d",&n,&m)){

		if(m==0){

			puts("1");

			puts("1");

			continue;

		}

		memset(deg,0,sizeof(deg));

		for(int i=0;i<m;++i){

			scanf("%d%d",&e[i][0],&e[i][1]);

			deg[e[i][0]]++;

			deg[e[i][1]]++;

		}

		double l=0,r=m;

		while(r-l>eps){

			double mid = (l+r)/2;

			if(jud(mid)) l=mid;

			else r=mid;

		}

		//printf("%lf\n",l);

		jud(l);

		sap.bfs(n+1);

		sort(ans.begin(),ans.end());

		printf("%d\n",ans.size());

		for(int i=0;i<ans.size();++i) printf("%d\n",ans[i]);

	}

	return 0;

}