#include<iostream>

#include<cstdio>

#include<cstdlib>

#include<algorithm>

#include<cstring>

#define inf 0x7fffffff

#define ll long long

using namespace std;

inline ll read()

{

    ll x=,f=;char ch=getchar();

    while(ch>''||ch<''){if(ch=='-')f=-;ch=getchar();}

    while(ch>=''&&ch<=''){x=x*+ch-'';ch=getchar();}

    return x*f;

}

int n,m,cnt,ans;

int head[],d[],q[],col[],hash[];

bool vis[];

struct data{int to,next;}e[];

void ins(int u,int v)

{e[++cnt].to=v;e[cnt].next=head[u];head[u]=cnt;}

int main()

{

    n=read();m=read();

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

    {

        int u=read(),v=read();

        ins(u,v);ins(v,u);

    }

    for(int i=n;i;i--)

    {

        int t=;

        for(int j=;j<=n;j++)

        {

            if(!vis[j]&&d[j]>=d[t])t=j;

        }

        vis[t]=;q[i]=t;

        for(int j=head[t];j;j=e[j].next)

            d[e[j].to]++;

    }

    for(int i=n;i>;i--)

    {

        int t=q[i];

        for(int j=head[t];j;j=e[j].next)hash[col[e[j].to]]=i;

        int j;

        for(j=;;j++)if(hash[j]!=i)break;

        col[t]=j;

        if(j>ans)ans=j;

    }

    printf("%d",ans);

    return ;

}