#include <bits/stdc++.h>
typedef long long ll;
using namespace std;
const int MX = 1e5 + 69;
int dis[MX];
multiset<int> nigga;
vector<int> adj[MX];
int bfs(int root)
{
    nigga.clear();
    memset(dis,-1,sizeof dis);
    queue<int> q;
    q.push(root);
    dis[root] =0;
    int mx =-1,opt=1e9+6;
    while(!q.empty())
    {
        int nxt = q.front();
        q.pop();
        for(auto u :adj[nxt])
        {
            if(dis[u]!=-1)continue;
            dis[u] = dis[nxt] +1;
            if(dis[u]>mx)
            {
                mx = dis[u];
                opt = u;
            }
             if(u!=root&&adj[u].size()==1)
                    nigga.insert(dis[u]);
            q.push(u);
        }
    }
    return opt;
}
int main()
{
    int n;
    cin>>n;
    if(n==1)
    {
        cout<<0;return 0;
    }
    for(int i=1;i<n;i++)
    {
        int a,b;
        scanf("%d%d",&a,&b);
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    int uu = bfs(bfs(1));
    auto u = nigga.end();
    u--;
    int ans = *u;
    if(u!=nigga.begin())
    {
        u--;
        ans -= *u;
    }
    bfs(uu);
    u = nigga.end();
    u--;
    int res = *u;
    if(u!=nigga.begin())
    {
        u--;
        res -= *u;
    }
    if(ans+res>=n)ans=max(ans,res);
    else ans =res + ans;
    cout<<ans<<endl;
}