#include<iostream>

 using namespace std;

 const int N = 1e6+;

 struct EDGE {

     int to, pre;

 }edge[*N];

 int n, tot=, head[N], first[N], second[N], ans=;

 void read(int &x) {

     int f = ; x = ;

     char ch = getchar();

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

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

     x *= f;

 }

 void add_edge(int a, int b)

 {

     edge[tot].to = b;

     edge[tot].pre = head[a];

     head[a] = tot++;

 }

 void dfs(int k, int pre)

 {

     for(int i=head[k]; i; i=edge[i].pre) {

         int to = edge[i].to;

         if(to == pre) continue;

         dfs(to, k);

         if(first[k] < first[to]+) {

             second[k] = first[k];

             first[k] = first[to]+;

         }

         else

             second[k] = max(second[k], first[to]+);

     }

     ans = max(ans, first[k]+second[k]);

 }

 int main()

 {

     read(n);

     for(int a,b,i=; i<n; i++) {

         read(a); read(b);

         add_edge(a,b);

         add_edge(b,a);

     }

     dfs(, );

     cout<<ans+<<endl;

     return ;

 }