#include <bits/stdc++.h>
using namespace std;
using ll=long long;
using ld=long double;
using P=pair<ll,ll>;
using V=vector<ll>;
#define rep(i,n) for(int i=0;i<n;i++)
#define REP(i,n) for(int i=1;i<=n;i++)

V k(202020,-1);

int root(int x){
    if(k[x]<0) return x;
    return k[x]=root(k[x]);
}

void unite(int x,int y){
    x=root(x); y=root(y);
    if(x==y) return;
    k[y]=x;
}

int main(){
    int n,m;
    cin >> n >> m;
    V u(m),v(m);
    rep(i,m){
        cin >> u[i] >> v[i];
        u[i]--;
        v[i]--;
    }
    reverse(u.begin(),u.end());
    reverse(v.begin(),v.end());
    
    V a(n); ll ans=0;
    rep(i,m){
        a[root(u[i])]=a[root(v[i])]=max(a[root(u[i])],a[root(v[i])])+1;
        unite(u[i],v[i]);
    }
    rep(i,n) ans=max(ans,a[i]);
    cout << ans << endl;
}