#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001
int N;
vector<vector<int>> E;
vector<int> sz,dpA,dpB;

void dfs(int cur,int p){
	sz[cur] = 1;
	rep(i,E[cur].size()){
		int to = E[cur][i];
		if(to==p)continue;
		dfs(to,cur);
		sz[cur] += sz[to];
	}
}

void dfs1(int cur,int p){
	dpA[cur] = 1;
	rep(i,E[cur].size()){
		int to = E[cur][i];
		if(to==p)continue;
		dfs1(to,cur);
	}
	
	rep(i,E[cur].size()){
		int to = E[cur][i];
		if(to==p)continue;
		dpB[cur] = max(dpB[cur],dpA[to] + 1);
		dpB[cur] = max(dpB[cur],dpB[to]);
		dpA[cur] = max(dpA[cur],dpA[to]);
		if(dpA[to]!=sz[to]){
			dpA[cur] = max(dpA[cur],dpA[to]+2);
		}
	}
	vector<int> dp(4,0);
	rep(i,E[cur].size()){
		int to = E[cur][i];
		if(to==p)continue;
		vector<int> ndp(4,0);
		rep(j,4){
			ndp[j] = max(ndp[j],dp[j]);
			rep(k,2){
				if((j>>k)&1)continue;
				ndp[j|(1<<k)] = max(ndp[j|(1<<k)], dp[j] + dpA[to]);
			}
		}
		swap(dp,ndp);
	}
	dpA[cur] = max(dpA[cur],dp[3] + 1);
	dp.assign(4,0);
	rep(i,E[cur].size()){
		int to = E[cur][i];
		if(to==p)continue;
		vector<int> ndp(4,0);
		rep(j,4){
			ndp[j] = max(ndp[j],dp[j]);
			rep(k,2){
				if((j>>k)&1)continue;
				if(k==0)ndp[j|(1<<k)] = max(ndp[j|(1<<k)], dp[j] + dpA[to]);
				else ndp[j|(1<<k)] = max(ndp[j|(1<<k)], dp[j] + dpB[to]);
			}
		}
		swap(dp,ndp);
	}
	dpB[cur] = max(dpB[cur],dp[3] + 1);
}
		

int main(){
	
	cin>>N;
	E.resize(N);
	rep(i,N-1){
		int u,v;
		cin>>u>>v;
		u--;v--;
		E[u].push_back(v);
		E[v].push_back(u);
	}
	
	sz.resize(N,0);
	dpA.resize(N,0);
	dpB.resize(N,0);
	dfs(0,-1);
	dfs1(0,-1);
	
	int ans = 0;
	rep(i,N){
		ans = max(ans,dpA[i]);
		ans = max(ans,dpB[i]);
	}
	/*
	rep(i,N){
		cout<<dpA[i]<<endl;
	}
	*/
	cout<<ans<<endl;
	
	return 0;
}