#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
vector<int> v[100005];
int dp[100005],ans=0;
void dfs(int node,int pnode)
{
    vector<int> tmp;
    for (int i=0;i<v[node].size();i++)
    {
        if (v[node][i]!=pnode)
        {
            dfs(v[node][i],node);
            tmp.push_back(dp[v[node][i]]);
        }
    }
    sort(tmp.begin(),tmp.end());
    if (tmp.size()==0)
    return;
    dp[node]=tmp[tmp.size()-1]+1;
    if (tmp.size()==1)
    ans=max(ans,dp[node]);
    else
    ans=max(ans,tmp[tmp.size()-1]+tmp[tmp.size()-2]+2);
}
int main()
{
    int n;
    cin >> n;
    for (int i=1;i<n;i++)
    {
        int a,b;
        cin >> a >> b;
        v[a].push_back(b);
        v[b].push_back(a);
    }
    dfs(1,0);
    cout << ans;
}