#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<queue>
using namespace std;
#define Maxn 510
#define Maxm 1247501+100 

int n;

struct node
{
	int x,y,next;
}t[Maxm*2];
int first[Maxn],len;

void ins(int x,int y)
{
	t[++len].x=x;t[len].y=y;
	t[len].next=first[x];first[x]=len;
}

int fa[Maxn],nt[Maxn],mark[Maxn],match[Maxn];
int vis[Maxn],nw;
int ffa(int x)
{
	if(fa[x]!=x) fa[x]=ffa(fa[x]);
	return fa[x];
}

int merge(int x,int y)
{
	fa[ffa(x)]=ffa(y);
}

queue<int > q;

//找环
int LCA(int x,int y)
{
	nw++;
	while(1)
	{
		if(x)
		{
			x=ffa(x);
			if(vis[x]==nw) return x;
			vis[x]=nw;
			if(match[x]) x=nt[match[x]];
			else x=0;
		}
		int tt=x;x=y;y=tt;
	}
}

//奇环缩点
void shrink(int x,int rt)
{
	while(x!=rt)
	{
		int y=match[x],z=nt[y];
		if(ffa(z)!=rt) nt[z]=y;
		if(mark[y]==2) {q.push(y);mark[y]=1;}
		if(mark[z]==2) {q.push(z);mark[z]=1;}
		merge(x,y);merge(y,z);
		x=z;
	}
}

void augment(int now)
{
	nw=0;
	for(int i=1;i<=n;i++)
		nt[i]=0,vis[i]=0,mark[i]=0,fa[i]=i;
	while(!q.empty()) q.pop();
	q.push(now);mark[now]=1;
	while(!q.empty())
	{
		int x=q.front();q.pop();
		if(match[now]) return;//当前搜索节点找到增广路
		for(int i=first[x];i;i=t[i].next)
		{
			int y=t[i].y;
			if(match[x]==y||ffa(x)==ffa(y)) continue;
			if(mark[y]==2) continue;
			//奇环缩点
			if(mark[y]==1)
			{
				int rt=LCA(x,y);
				if(ffa(x)!=rt) nt[x]=y;
				if(ffa(y)!=rt) nt[y]=x;
				
				shrink(x,rt);shrink(y,rt);
			}
			//增广
			else if(!match[y])
			{
				nt[y]=x;
				for(int j=y;j;)
				{
					int k=nt[j],z=match[k];
					match[j]=k;match[k]=j;
					j=z;
				}
				break;
			}
                        //之前匹配过
			else
			{
				nt[y]=x;
				q.push(match[y]);
				mark[match[y]]=1;
				mark[y]=2;
			}
		}
	}	
}

int main()
{
	int m;
	scanf("%d%d",&n,&m);
	len=0;
	memset(first,0,sizeof(first));
	for(int i=1;i<=m;i++)
	{
		int x,y;
		scanf("%d%d",&x,&y);
		ins(x,y);ins(y,x);
	}
	int ans=0;
	memset(match,0,sizeof(match));
	for(int i=1;i<=n;i++) if(!match[i]) augment(i);
	for(int i=1;i<=n;i++) if(match[i]) ans++;
	ans/=2;
	printf("%d\n",ans);
	for(int i=1;i<=n;i++) printf("%d ",match[i]);
	printf("\n");
	return 0;
}