#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
vector<vector<int>> adj;
vector<int> dp;
void dfs(int v, int parent){
	//no return;
	for(auto x : adj[v]){
		if(x == parent) continue;
		dfs(x, v);
		dp[v] = max(dp[v], dp[x] + 1);
	}
}

int main(){
	int n;
	cin >> n;
	adj.resize(n, vector<int>());
	dp.resize(n, 1);
	vector<bool> visited(n, false);
	//这里节点从0开始到n - 1 
	for(int i = 0; i < n - 1; i++){
		int a, b;
		cin >> a >> b;
		adj[a].push_back(b);
		adj[b].push_back(a);
	}
	dfs(0, -1);
	int mmax = 0;
	if(adj[0].size() == 1) cout << dp[0] << endl;
	else{
		vector<int> tmp;
		for(auto x : adj[0]){
			tmp.push_back(dp[x]);
		}
		sort(tmp.begin(), tmp.end());
		mmax = *(tmp.end() - 1) + *(tmp.end() - 2);
		cout << mmax + 1<< endl;
	}
	return 0;
}
/*
7
0 1
0 2
1 3
1 4
2 5
2 6

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