# include<bits/stdc++.h>

using namespace std;

vector <int> v[20000];
int dp[20000],n,sol=-1001;
char viz[20000];
void dfs(int p)
{	
	if(viz[p]) return; 
	viz[p]=1;
	int s = v[p].size();
	//cout<<"p="<<p<<'\n';
	for(int f=0;f<s;f++){
	 dfs(v[p][f]);
	 if(viz[v[p][f]]==2)
	 dp[p]=max(dp[p],dp[v[p][f]]+dp[p]);
	}
	sol=max(sol,dp[p]);
	viz[p]=2;
	//cout<<"sol = "<<sol<<'\n';
	//for(int i=1;i<=n;i++) cout<<dp[i]<<' ';
	//cout<<'\n';
}

int main(){
	ifstream fin("asmax.in");
	ofstream fout("asmax.out");
	fin>>n;
	memset(viz,0,n);
	for(int i=1;i<=n;i++)
		fin>>dp[i];
	/*for(int i=1;i<=n;i++)
		cout<<dp[i]<<' ';
	cout<<'\n';	*/	
	int a,b;
	for(int i=1;i<n;i++){
		fin>>a>>b;
		v[a].push_back(b);
		v[b].push_back(a);
	}
	/*for(int i=1;i<=n;i++){
		cout<<i<<": ";
		for(int j=0;j<v[i].size();j++)
		 cout<<v[i][j]<<' ';
	cout<<'\n';
	}*/
	int x = rand()%n+1;
	dfs(x);
	fout<<sol;
	return 0;
}