#include<bits/stdc++.h>
#include<atcoder/all>
using namespace std;
namespace my{
#define eb emplace_back
#define LL(...) ll __VA_ARGS__;lin(__VA_ARGS__)
#define FO(n) for(ll ij=n;ij--;)
#define FOR(i,...) for(auto[i,i##stop,i##step]=range(0,__VA_ARGS__);i<i##stop;i+=i##step)
#define fo(i,...) FO##__VA_OPT__(R)(i __VA_OPT__(,__VA_ARGS__))
#define fe(a,i,...) for(auto&&__VA_OPT__([)i __VA_OPT__(,__VA_ARGS__]):a)
#define single_testcase void solve();}int main(){my::io();my::solve();}namespace my{
void io(){cin.tie(nullptr)->sync_with_stdio(0);cout<<fixed<<setprecision(15);}
using ll=long long;
template<class...A>constexpr auto range(bool s,A...a){array<ll,3>r{0,0,1};ll I=0;((r[I++]=a),...);if(!s&&I==1)swap(r[0],r[1]);r[0]-=s;return r;}
constexpr char nl=10;
constexpr char sp=32;
bool amax(auto&a,const auto&b){return a<b?a=b,1:0;}
auto max(const auto&...a){return max(initializer_list<common_type_t<decltype(a)...>>{a...});}

template<class A,class B>struct pair{
  A a;B b;
  pair()=default;
  pair(A a,B b):a(a),b(b){}
  pair(const std::pair<A,B>&p):a(p.first),b(p.second){}
  auto operator<=>(const pair&)const=default;
  friend ostream&operator<<(ostream&o,const pair&p){return o<<p.a<<sp<<p.b;}
};

template<class F=less<>>auto&sort(auto&a,const F&f={}){ranges::sort(a,f);return a;}

template<class T,class U>ostream&operator<<(ostream&o,const std::pair<T,U>&p){return o<<p.first<<sp<<p.second;}

template<class V>concept vectorial=is_base_of_v<vector<typename V::value_type>,V>;
template<class T>struct vec_attr{using core_type=T;static constexpr int d=0;};
template<vectorial V>struct vec_attr<V>{using core_type=typename vec_attr<typename V::value_type>::core_type;static constexpr int d=vec_attr<typename V::value_type>::d+1;};
template<class T>using core_t=vec_attr<T>::core_type;
template<class V>istream&operator>>(istream&i,vector<V>&v){fe(v,e)i>>e;return i;}
template<class V>ostream&operator<<(ostream&o,const vector<V>&v){fe(v,e)o<<e<<string(&e!=&v.back(),vectorial<V>?nl:sp);return o;}

template<class V>struct vec:vector<V>{
  using vector<V>::vector;
  vec(const vector<V>&v){vector<V>::operator=(v);}

  vec&operator^=(const vec&u){this->insert(this->end(),u.begin(),u.end());return*this;}
  vec operator^(const vec&u)const{return vec{*this}^=u;}
  vec&operator++(){fe(*this,e)++e;return*this;}
  vec&operator--(){fe(*this,e)--e;return*this;}
  vec operator-()const{vec v=*this;fe(v,e)e=-e;return v;}

  auto scan(const auto&f)const{pair<core_t<V>,bool>r{};fe(*this,e)if constexpr(!vectorial<V>)r.b?f(r.a,e),r:r={e,1};else if(auto s=e.scan(f);s.b)r.b?f(r.a,s.a),r:r=s;return r;}
  auto max()const{return scan([](auto&a,const auto&b){a<b?a=b:0;}).a;}
};

void lin(auto&...a){(cin>>...>>a);}
template<char c=sp>void pp(const auto&...a){ll n=sizeof...(a);((cout<<a<<string(--n>0,c)),...);cout<<nl;}

void dec(auto&...a){((--a),...);}

struct dsu{
  ll n;
  vec<ll>d;
  dsu(ll n):n(n),d(n,-1){}

  ll leader(ll a){
    assert(0<=a&&a<n);
    if(d[a]<0)return a;
    return d[a]=leader(d[a]);
  }

  ll size(ll a){
    return-d[leader(a)];
  }

  ll merge(ll a,ll b){
    ll x=leader(a),y=leader(b);
    if(x==y)return x;
    if(-d[x]<-d[y])swap(x,y);
    d[x]+=d[y],d[y]=x;
    return x;
  }
};

template<class WT>struct edge{
  ll from,to;
  WT wt;
  ll id;
  edge()=default;
  edge(ll from,ll to,WT wt=1,ll id=-1):from(from),to(to),wt(wt),id(id){}
  auto operator<=>(const edge&e)const{return wt<=>e.wt;}
  friend ostream&operator<<(ostream&o,const edge&e){return o<<"(to "<<e.to<<", wt "<<e.wt<<")";}
};

template<class WT>struct graph{
  vec<vec<edge<WT>>>edges;

  graph()=default;
  graph(ll n):edges(n){}

  decltype(auto)operator[](ll i){return edges[i];}
  decltype(auto)operator[](ll i)const{return edges[i];}

  ll size()const{return edges.size();}

  friend ostream&operator<<(ostream&o,const graph&g){
    fo(u,g.size()){
      o<<"from "<<u<<": ";
      fo(j,g[u].size())o<<g[u][j]<<string(j!=g[u].size()-1,sp);
      o<<nl;
    }
    return o;
  }

  template<class...A>void add_edge(ll a,A&&...b){edges[a].eb(a,std::forward<A>(b)...);}
  void add_edge(const edge<WT>&e){edges[e.from].eb(e);}

  vec<edge<WT>>get_edges()const{
    vec<edge<WT>>res;
    fo(u,size())fe(edges[u],e)res.eb(e);
    return res;
  }
};

single_testcase
void solve(){
  LL(N,M);
  graph<ll>G(N);
  fo(i,M){
    LL(a,b);dec(a,b);
    G.add_edge(a,b,1,i);
    G.add_edge(b,a,1,i);
  }

  dsu uf(N);
  vec<ll>dp(N);
  auto es=G.get_edges();
  sort(es,[&](auto&a,auto&b){return a.id>b.id;});
  fe(es,e){
    if(e.from>e.to)continue;
    ll nl=uf.merge(e.from,e.to);
    amax(dp[nl],max(dp[uf.leader(e.from)],dp[uf.leader(e.to)])+1);
  }
  pp(dp.max());
}}