#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <tuple>
#include <cmath>
#include <numeric>
#include <functional>
#include <cassert>

#define debug_value(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << #x << "=" << x << endl;
#define debug(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << x << endl;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

using namespace std;
typedef long long ll;

template<typename T>
vector<vector<T>> vec2d(int n, int m, T v){
    return vector<vector<T>>(n, vector<T>(m, v));
}

template<typename T>
vector<vector<vector<T>>> vec3d(int n, int m, int k, T v){
    return vector<vector<vector<T>>>(n, vector<vector<T>>(m, vector<T>(k, v)));
}

template<typename T>
void print_vector(vector<T> v, char delimiter=' '){
    if(v.empty()) {
        cout << endl;
        return;
    }
    for(int i = 0; i+1 < v.size(); i++) cout << v[i] << delimiter;
    cout << v.back() << endl;
}

vector<int> tree_diameter(vector<vector<int>> g){
    int n = g.size();
    vector<bool> used(n, false);
    vector<int> dist(n);
    auto clear = [&](){
        for(int i = 0; i < n; i++) used[i] = false;
    };
    auto dfs = [&](auto&& f, int v, int d) -> void{
        used[v] = true;
        dist[v] = d;
        for(int to : g[v]){
            if(!used[to]) f(f, to, d+1);
        }
    };
    dfs(dfs, 0, 0);
    int s = 0;
    for(int i = 0; i < n; i++){
        if(dist[s] < dist[i]) s = i;
    }
    clear();
    dfs(dfs, s, 0);
    int t = 0;
    for(int i = 0; i < n; i++){
        if(dist[t] < dist[i]) t = i;
    }
    int v = t;
    vector<int> path;
    path.push_back(t);
    while(v != s){
        for(int to : g[v]){
            if(dist[to] == dist[v]-1) {
                v = to;
                break;
            }
        }
        path.push_back(v);
    }
    return path;
}

void calc_depth(int v, int par, vector<vector<int>> &g, vector<int> &max_depth, vector<bool> &is_in_diameter, int d){
    max_depth[v] = d;
    for(int to: g[v]){
        if(to == par) continue;
        if(is_in_diameter[to]) calc_depth(to, v, g, max_depth, is_in_diameter, d);
        else {
            calc_depth(to, v, g, max_depth, is_in_diameter, d+1);
            chmax(max_depth[v], max_depth[to]);
        }
    }
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    int n; cin >> n;
    vector<vector<int>> g(n);
    for(int i = 0; i < n-1; i++){
        int u, v; cin >> u >> v; u--; v--;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    auto diam = tree_diameter(g);
    vector<bool> is_in_diamerer(n);
    for(int v: diam) is_in_diamerer[v] = true;
    int s = diam[0], t = diam.back();
    vector<int> max_depth_s(n), max_depth_t(n);
    calc_depth(s, -1, g, max_depth_s, is_in_diamerer, 0);
    calc_depth(t, -1, g, max_depth_t, is_in_diamerer, 0);
    assert(max_depth_s == max_depth_t);
    int r = diam.size()-1;
    vector<int> lr(r+1), rr(r+1);
    for(int i = 1; i < r; i++){
        int u = diam[i];
        lr[i] = max(lr[i-1], max_depth_s[u]+i);
    }
    for(int i = r-1; i > 0; i--){
        int u = diam[i];
        rr[i] = max(rr[i+1], max_depth_t[u]+(r-i));
    }
    // print_vector(lr);
    // print_vector(rr);
    int ans = r;
    for(int i = 0; i < r; i++){
        chmin(ans, max({lr[i], rr[i+1], (lr[i]+1)/2+(rr[i+1]+1)/2+1}));
        // debug_value((lr[i]+1)/2+(rr[i+1]+1)/2+1)
    }
    cout << ans << endl;
}