#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define ALL(v) v.begin(),v.end()
typedef long long ll;

#include <bits/stdc++.h>
using namespace std;

class Dis{
  public:
  vector<ll> rank,p,siz;
  
  Dis(int s){
    rank.resize(s,0);
    p.resize(s,0);
    siz.resize(s,1);
    rep(i,s) makeSet(i);
  }
  
  void makeSet(int x){
    p[x]=x;
    rank[x]=0;
  }
  
  bool same(int x,int y){
    return findSet(x)==findSet(y);
  }
  
  void unite(int x,int y){
    if(same(x,y)) return;
    link(findSet(x),findSet(y));
  }
  
  void link(int x,int y){
    if(rank[x]>rank[y]){
      p[y]=x;
      siz[x]+=siz[y];
    }
    else{
      p[x]=y;
      siz[y]+=siz[x];
      if(rank[x]==rank[y]) rank[y]++;
    }
  }
  
  int findSet(int x){
    if(x != p[x]) p[x]=findSet(p[x]);
    return p[x];
  }
  
  int size(int x){
    return siz[findSet(x)];
  }
};

vector<int> G[200200];
int A[200200];

int main(){
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);

  int n,m;
  cin>>n>>m;
  vector<int> U(m),V(m);
  rep(i,m){
    cin>>U[i]>>V[i];
    U[i]--,V[i]--;
  }
  
  Dis ds=Dis(m);
  
  int ma=0;
  for(int i=m-1;i>=0;i--){
    int t=0;
    if(G[U[i]].size()) t=max(t,A[ds.findSet(G[U[i]][0])]);
    if(G[V[i]].size()) t=max(t,A[ds.findSet(G[V[i]][0])]);
    if(G[U[i]].size()) ds.unite(i,G[U[i]][0]);
    if(G[V[i]].size()) ds.unite(i,G[V[i]][0]);
    ma=max(ma,t+1);
    A[ds.findSet(i)]=t+1;
    G[U[i]].push_back(i),G[V[i]].push_back(i);
  }
  cout<<ma<<endl;

  return 0;
}