#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 998244353;
// constexpr int MOD = 1000000007;
constexpr int DY4[]{1, 0, -1, 0}, DX4[]{0, -1, 0, 1};
constexpr int DY8[]{1, 1, 0, -1, -1, -1, 0, 1};
constexpr int DX8[]{0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U>
inline bool chmax(T& a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U>
inline bool chmin(T& a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

int main() {
  int n; cin >> n;
  vector<vector<int>> graph(n);
  REP(_, n - 1) {
    int u, v; cin >> u >> v; --u; --v;
    graph[u].emplace_back(v);
    graph[v].emplace_back(u);
  }
  vector<vector<tuple<int, int, int>>> dp(n);
  const auto dfs1 = [&](auto dfs1, const int par, const int ver) -> void {
    if (par != -1) graph[ver].erase(ranges::find(graph[ver], par));
    for (const int e : graph[ver]) {
      dfs1(dfs1, ver, e);
      int diam = 0;
      for (const int d : dp[e] | views::elements<1>) chmax(diam, d);
      if (!dp[e].empty()) chmax(diam, get<0>(dp[e].front()));
      if (dp[e].size() >= 2) chmax(diam, get<0>(dp[e][0]) + get<0>(dp[e][1]));
      dp[ver].emplace_back(dp[e].empty() ? 1 : get<0>(dp[e].front()) + 1, diam, e);
    }
    if (!dp[ver].empty()) {
      ranges::sort(dp[ver], greater<int>(), [](const tuple<int, int, int>& x) -> int { return get<0>(x); });
    }
  };
  dfs1(dfs1, -1, 0);
  // REP(i, n) {
  //   cout << i + 1 << ':';
  //   for (const auto& [root, diam, e] : dp[i]) {
  //     cout << " (" << root << ',' << diam << ',' << e + 1 << ')';
  //   }
  //   cout << '\n';
  // }
  int ans = INF;
  const auto dfs2 = [&](auto dfs2, const int par, const int ver) -> void {
    ranges::sort(dp[ver], greater<int>(), [](const tuple<int, int, int>& x) -> int { return get<0>(x); });
    const int ch = dp[ver].size();
    vector<int> from_l(ch, 0), from_r(ch, 0);
    FOR(i, 1, ch) from_l[i] = max(from_l[i - 1], get<1>(dp[ver][i - 1]));
    for (int i = ch - 2; i >= 0; --i) {
      from_r[i] = max(from_r[i + 1], get<1>(dp[ver][i + 1]));
    }
    REP(i, ch) {
      if (get<2>(dp[ver][i]) == par) continue;
      const int through = [&]() -> int {
        if (ch == 1) return 0;
        if (ch == 2) return get<0>(dp[ver][i == 0 ? 1 : 0]);
        if (i == 0) return get<0>(dp[ver][1]) + get<0>(dp[ver][2]);
        if (i == 1) return get<0>(dp[ver][0]) + get<0>(dp[ver][2]);
        return get<0>(dp[ver][0]) + get<0>(dp[ver][1]);
      } ();
      const int x = max({from_l[i], from_r[i], through}), y = get<1>(dp[ver][i]);
      chmin(ans, max({x, y, (x + 1) / 2 + (y + 1) / 2 + 1}));
      dp[get<2>(dp[ver][i])].emplace_back(ch == 1 ? 1 : get<0>(dp[ver][i == 0 ? 1 : 0]) + 1, x, ver);
      dfs2(dfs2, ver, get<2>(dp[ver][i]));
    }
  };
  dfs2(dfs2, -1, 0);
  // REP(i, n) {
  //   cout << i + 1 << ':';
  //   for (const auto& [root, diam, e] : dp[i]) {
  //     cout << " (" << root << ',' << diam << ',' << e + 1 << ')';
  //   }
  //   cout << '\n';
  // }
  cout << ans << '\n';
  return 0;
}