// bzoj1006#include<algorithm>#include<iostream>#include<cstdlib>#include<cstring>#include<cstdio>#include<cmath>#include<queue>#define LL long long#define inf 1<<30#define Pi acos(-1.0)#define free(a) freopen(a".in","r",stdin),freopen(a".out","w",stdout);using namespace std;const int maxn=10010,maxm=1000010;int label[maxn],vis[maxn],head[maxn],c[maxn],a[maxn];int n,m,cnt;struct edge {int to,next;}e[maxm<<1];struct data {	int id,w;	friend bool operator < (const data a,const data b) {		return a.w<b.w;	}};void link(int u,int v) {	e[++cnt]=(edge){v,head[u]};head[u]=cnt;	e[++cnt]=(edge){u,head[v]};head[v]=cnt;}void color(int x) {	for (int i=head[x];i;i=e[i].next) vis[c[e[i].to]]=x;	for (int i=1;i<=cnt;i++) if (vis[i]!=x) {c[x]=i;break;}	if (!c[x]) c[x]=++cnt;}int main() {	scanf("%d%d",&n,&m);	for (int u,v,i=1;i<=m;i++) {		scanf("%d%d",&u,&v);		link(u,v);	}	priority_queue<data> q;q.push((data){n,0});	int tot=0;	while (!q.empty()) {		int x=q.top().id;q.pop();		if (vis[x]) continue;		vis[x]=1;a[++tot]=x;		for (int i=head[x];i;i=e[i].next) if (!vis[e[i].to]) {				label[e[i].to]++;				q.push((data){e[i].to,label[e[i].to]});			}	}	memset(vis,0,sizeof(vis));	cnt=0;	for (int i=1;i<=n;i++) color(a[i]);	printf("%d",cnt);    return 0;}