#include <bits/stdc++.h>
using namespace std;
template <typename TH>
void _dbg(const char* sdbg, TH h) {
  cerr << sdbg << "=" << h << "\n";
}
template <typename TH, typename... TA>
void _dbg(const char* sdbg, TH h, TA... t) {
  while (*sdbg != ',') {
    cerr << *sdbg++;
  }
  cerr << "=" << h << ",";
  _dbg(sdbg + 1, t...);
}
template <class C>
void mini(C& a4, C b4) {
  a4 = min(a4, b4);
}
template <class C>
void maxi(C& a4, C b4) {
  a4 = max(a4, b4);
}
template <class T1, class T2>
ostream& operator<<(ostream& out, pair<T1, T2> pair) {
  return out << "(" << pair.first << ", " << pair.second << ")";
}
template <class A, class B, class C>
struct Triple {
  A first;
  B second;
  C third;
  bool operator<(const Triple& t) const {
    if (first != t.first) return first < t.first;
    if (second != t.second) return second < t.second;
    return third < t.third;
  }
};
template <class T>
void ResizeVec(T&, vector<long long>) {}
template <class T>
void ResizeVec(vector<T>& vec, vector<long long> sz) {
  vec.resize(sz[0]);
  sz.erase(sz.begin());
  if (sz.empty()) {
    return;
  }
  for (T& v : vec) {
    ResizeVec(v, sz);
  }
}
template <class A, class B, class C>
ostream& operator<<(ostream& out, Triple<A, B, C> t) {
  return out << "(" << t.first << ", " << t.second << ", " << t.third << ")";
}
template <class T>
ostream& operator<<(ostream& out, vector<T> vec) {
  out << "(";
  for (auto& v : vec) out << v << ", ";
  return out << ")";
}
template <class T>
ostream& operator<<(ostream& out, set<T> vec) {
  out << "(";
  for (auto& v : vec) out << v << ", ";
  return out << ")";
}
template <class L, class R>
ostream& operator<<(ostream& out, map<L, R> vec) {
  out << "(";
  for (auto& v : vec) out << v << ", ";
  return out << ")";
}
const long long N = 1e6 + 5;
vector<long long> slo[N];
long long dp_int[N];
long long dp_ind[N];
long long best;
void Dfs(long long v, long long p) {
  vector<long long> biggest_sons_int;
  vector<long long> biggest_sons_all;
  long long has_par = (p != -1);
  maxi(dp_ind[v], 1ll);
  maxi(dp_int[v], ((long long)(slo[v]).size()) - has_par);
  for (auto nei : slo[v]) {
    if (nei == p) {
      continue;
    }
    Dfs(nei, v);
    biggest_sons_all.push_back(max(dp_int[nei], dp_ind[nei]));
    biggest_sons_int.push_back(dp_int[nei]);
    long long bonus = (((long long)(slo[v]).size()) - 1) - has_par;
    maxi(dp_int[v], max(dp_int[nei], dp_ind[nei]) + bonus);
    maxi(dp_ind[v], dp_int[nei] + 1);
  }
  sort((biggest_sons_int).begin(), (biggest_sons_int).end());
  reverse((biggest_sons_int).begin(), (biggest_sons_int).end());
  sort((biggest_sons_all).begin(), (biggest_sons_all).end());
  reverse((biggest_sons_all).begin(), (biggest_sons_all).end());
  if (((long long)(biggest_sons_int).size()) >= 2) {
    maxi(best, biggest_sons_int[0] + biggest_sons_int[1] + 1);
  }
  if (((long long)(biggest_sons_all).size()) >= 2) {
    maxi(best, biggest_sons_all[0] + biggest_sons_all[1] +
                   ((long long)(slo[v]).size()) - 2);
  }
  maxi(best, dp_ind[v]);
  maxi(best, dp_int[v] + has_par);
}
int32_t main() {
  ios_base::sync_with_stdio(0);
  cout << fixed << setprecision(10);
  if (0) cout << fixed << setprecision(10);
  cin.tie(0);
  long long n;
  cin >> n;
  for (long long i = (1); i <= (n - 1); ++i) {
    long long a, b;
    cin >> a >> b;
    slo[a].push_back(b);
    slo[b].push_back(a);
  }
  Dfs(1, -1);
  cout << best << endl;
  return 0;
}
