Seminar3

#include <algorithm>
#include <iostream>
#include <vector>

//        0
//   1      3   4
//   2      5
// 6 7 8

// 9
// 0 1   0 3   0 4   1 2   3 5   2 6   2 7   2 8

struct TreeNode {
  int Parent = 0;
  int Depth = 0;
  std::vector<int> Children;
};

void CalcDepth(std::vector<TreeNode>& nodes, int a) {
  for (auto x : nodes[a].Children) {
    CalcDepth(nodes, x);
    nodes[a].Depth = std::max(nodes[a].Depth, nodes[x].Depth + 1);
  }
}

int FindMaxPath(std::vector<TreeNode>& nodes) {
  int result = 0;
  for (auto& node : nodes) {
    if (node.Children.size() <= 1)
      result = std::max(result, node.Depth);
    else {
      std::sort(node.Children.begin(), node.Children.end(), [&nodes](int l, int r) {
        return nodes[l].Depth > nodes[r].Depth;
      });
      auto first = node.Children.begin();
      result = std::max(result, nodes[*first].Depth + nodes[*(first + 1)].Depth + 2);
    }
  }
  return result;
}

int main() {
  int n = 0;
  std::cin >> n;
  // Вектор из n узлов.
  std::vector<TreeNode> nodes(n);
  for (int i = 1; i < n; ++i) {
    int a = 0, aa = 0;
    std::cin >> a >> aa;
    if (a > aa) std::swap(a, aa);
    nodes[a].Children.push_back(aa);
    nodes[aa].Parent = a;
  }

  CalcDepth(nodes, 0);
  std::cout << FindMaxPath(nodes) << std::endl;
  return 0;
}