#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic pop
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  VVI to(n);
  rep(i, n - 1) {
    int u, v;
    cin >> u >> v;
    u--, v--;
    to[u].emplace_back(v);
    to[v].emplace_back(u);
  }
  auto dfs = [&](auto&& self, int u, int p) -> priority_queue<int> {
    priority_queue<int> q;
    for(int v: to[u]) if (v != p) {
      auto r = self(self, v, u);
      if (r.size() > q.size()) swap(r, q);
      while(r.size()) q.emplace(r.top()), r.pop();
    }
    int c = 1;
    rep(_, 2) if (q.size()) c += q.top(), q.pop();
    q.emplace(c);
    return q;
  };
  auto q = dfs(dfs, 0, -1);
  int ans = q.top();
  cout << ans << '\n';
}