#pragma GCC optimize("O3")
#include<bits/stdc++.h> 
using namespace std;
using ll=long long;
using P=pair<ll,ll>;
template<class T> using V=vector<T>; 
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
const ll inf=(1e18);
// const ll mod=998244353;
const ll mod=1000000007;
const vector<int> dy={-1,0,1,0},dx={0,-1,0,1};
struct __INIT{__INIT(){cin.tie(0);ios::sync_with_stdio(false);cout<<fixed<<setprecision(15);}} __init;
template<class T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; }
template<class T>void debag(const vector<T> &a){cerr<<"debag :";for(auto v:a)cerr<<v<<" ";cerr<<"\n";}
template<class T>void print(const vector<T> &a){for(auto v:a)cout<<v<<" ";cout<<"\n";}
int main(){
    int n;
    cin>>n;
    V<V<int>> g(n);
    for(int i=0;i<n-1;i++){
        int a,b;
        cin>>a>>b;
        --a;--b;
        g[a].emplace_back(b);
        g[b].emplace_back(a);
    }
    V<P> res(n);//最長,部分木の直径
    auto dfs1=[&](auto &&self,int cur,int par)->P{
        P val={0,0};
        V<ll> cp;
        for(int v:g[cur]){
            if(v==par)continue;
            P tmp=self(self,v,cur);
            cp.emplace_back(tmp.fi);
            chmax(val.fi,tmp.fi+1);
            chmax(val.se,tmp.se);
        }
        chmax(val.se,val.fi);
        if((int)cp.size()>=2){
            sort(all(cp),greater<ll>());
            chmax(val.se,cp[0]+cp[1]+2);
        }
        return res[cur]=val;
    };
    dfs1(dfs1,0,-1);
    ll ans=res[0].se;
    auto dfs2=[&](auto &&self,int cur,int par,P val)->void{
        if(par!=-1){
            chmin(ans,(res[cur].se+1)/2+(val.se+1)/2+1);
        }
        multiset<ll> tmp,tmp2;
        for(int v:g[cur]){
            if(v==par)continue;
            tmp.emplace(res[v].fi);
            tmp2.emplace(res[v].se);
        }
        tmp.emplace(val.fi);
        tmp2.emplace(val.se);
        for(int v:g[cur]){
            if(v==par)continue;
            P nval={0,0};
            tmp.erase(tmp.find(res[v].fi));
            tmp2.erase(tmp2.find(res[v].se));
            if((int)tmp.size()>=2){
                auto ite=tmp.end();
                ite--;ll v=*ite;
                ite--;v+=*ite;
                v+=2;
                chmax(nval.se,v);
            }
            nval.fi=*tmp.rbegin()+1;
            chmax(nval.se,*tmp2.rbegin());
            chmax(nval.se,nval.fi);
            self(self,v,cur,nval);
            tmp.emplace(res[v].fi);
            tmp2.emplace(res[v].se);
        }
    };
    dfs2(dfs2,0,-1,{-1,0});
    cout<<ans<<"\n";
}