#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<set>
#include<map>
#include<vector>
#include<queue>
using namespace std;
#define ll long long
#define MAXL 1200000
#define MAX 12000
inline int read()
{
    int x=0,t=1;char ch=getchar();
    while((ch<'0'||ch>'9')&&ch!='-')ch=getchar();
    if(ch=='-')t=-1,ch=getchar();
    while(ch<='9'&&ch>='0')x=x*10+ch-48,ch=getchar();
    return x*t;
}
struct Line{int v,next;}e[MAXL<<1];
int h[MAX],cnt=1;
inline void Add(int u,int v){e[cnt]=(Line){v,h[u]};h[u]=cnt++;}
vector<int> V[MAX];
int n,m,label[MAX],best,ans,Q[MAX],tot;
bool vis[MAX];
int main()
{
    n=read();m=read();
    for(int i=1,u,v;i<=m;++i)
    {
        u=read(),v=read();
        Add(u,v);Add(v,u);
    }
    for(int i=1;i<=n;++i)V[0].push_back(i);best=0;
    for(int i=1,now=0;i<=n;++i)
    {
        bool fl=false;
        while(!fl)
        {
            for(int j=V[best].size()-1;j>=0;--j)
                if(vis[V[best][j]])V[best].pop_back();
                else{fl=true;now=V[best][j];break;}
            if(!fl)--best;
        }
        Q[++tot]=now;vis[now]=true;
        for(int j=h[now];j;j=e[j].next)
            if(!vis[e[j].v])
                V[++label[e[j].v]].push_back(e[j].v),best=max(best,label[e[j].v]);
    }
    for(int i=1;i<=n;++i)ans=max(ans,label[i]+1);
    printf("%d\n",ans); 
}