#include<iostream>
#include<fstream>
#include<vector>
#include<queue>
#include<cstring>
using namespace std;vector<vector<int> > v;int c[1000001]={0},last=1,viz[1000001]={0},diametru=0;queue<int> q;void bfs(int nod){q.push(nod);c[nod]=0;viz[nod]=1;while(!q.empty()){int nodcurent=q.front();q.pop();for(int i=0;i<v[nodcurent].size();i++){if(viz[v[nodcurent][i]]==0){viz[v[nodcurent][i]]=1;c[v[nodcurent][i]]=c[nodcurent]+1;q.push(v[nodcurent][i]);last=v[nodcurent][i];diametru=c[v[nodcurent][i]];}}}}int main(){int n,m;ifstream f("darb.in");ofstream g("darb.out");f>>m;v = vector<vector<int> >(m+1);for(int x,y,i=0;i<m;i++){f>>x>>y;v[x].push_back(y);v[y].push_back(x);}bfs(1);memset(viz,0,sizeof viz);bfs(last);g<<diametru+1;f.close();g.close();}