1 /**************************************************************
 2     Problem: 1006
 3     User: Tunix
 4     Language: C++
 5     Result: Accepted
 6     Time:536 ms
 7     Memory:34996 kb
 8 ****************************************************************/
 9  
10 //BZOJ 1006
11 #include<vector>
12 #include<cstdio>
13 #include<cstdlib>
14 #include<cstring>
15 #include<iostream>
16 #include<algorithm>
17 #define rep(i,n) for(int i=0;i<n;++i)
18 #define F(i,j,n) for(int i=j;i<=n;++i)
19 #define D(i,j,n) for(int i=j;i>=n;--i)
20 using namespace std;
21  
22 int getint(){
23     int v=0,sign=1; char ch=getchar();
24     while(ch<‘0‘||ch>‘9‘) {if (ch==‘-‘) sign=-1; ch=getchar();}
25     while(ch>=‘0‘&&ch<=‘9‘) {v=v*10+ch-‘0‘; ch=getchar();}
26     return v*sign;
27 }
28 typedef long long LL;
29 const int N=100010,INF=~0u>>2;
30 /*******************tamplate********************/
31 struct List{
32     int to,next;
33 }table[4004004];
34 int head[N],tot; 
35 int n,m,ans,best,f[N],list[N],seq[N],color[N],mark[N];
36 bool v[N];
37 void add(int *h,int x,int y){
38     table[++tot].to=y;
39     table[tot].next=h[x];
40     h[x]=tot;
41 }
42 void MCS(){
43     int i,j;
44     F(i,1,n) add(list,0,i);
45     D(j,n,1){
46         while(1){
47             for(i=list[best];i;i=table[i].next){
48                 if (!v[table[i].to]) break;
49                 else list[best]=table[i].next;
50             }
51             if (i){
52                 int x=table[i].to;
53                 v[x]=1; seq[j]=x;
54                 for(i=head[x];i;i=table[i].next)
55                     if(!v[table[i].to]){
56                         f[table[i].to]++;
57                         add(list,f[table[i].to],table[i].to);
58                         best=max(best,f[table[i].to]);
59                     }
60                 break;
61             }else best--;
62         }
63     }
64 }
65 int main(){
66 #ifndef ONLINE_JUDGE
67     freopen("input.txt","r",stdin);
68 //  freopen("output.txt","w",stdout);
69 #endif
70     n=getint(); m=getint();
71     int x,y;
72     F(i,1,m){
73         x=getint(); y=getint();
74         add(head,x,y);
75         add(head,y,x);
76     }
77     MCS();
78     D(j,n,1){
79         int x=seq[j],i;
80         for(int i=head[x];i;i=table[i].next)
81             mark[ color[table[i].to] ]=j;
82         for(i=1;i<=n && mark[i]==j;i++);
83         color[x]=i;
84         ans=max(ans,i);
85     }
86     printf("%d\n",ans);
87     return 0;
88 }