#include <cstdio>
#include <vector>
using namespace std;
const int N = 16005;
const int INF = 2000000000;
vector <int> v[N];
int d[N];
void DFS(int nod, int tata){
    for(auto it : v[nod])
    {
        if(it != tata)
        {
            DFS(it , nod);
        }
    }
    for(auto it : v[nod])
    {
        if(it != tata)
        {
            d[nod] = max(d[nod] , d[it] + d[nod]);
        }
    }
}

int main()
{
    int n, i, x, y;
    freopen("asmax.in","r",stdin);
    freopen("asmax.out","w",stdout);
    scanf("%d", &n);
    for(i = 1;i <= n; ++i){
        scanf("%d", &d[i]);
    }
    for(i = 1;i <= n - 1; ++i)
    {
        scanf("%d%d", &x, &y);
        v[x].push_back(y);
        v[y].push_back(x);
    }
    DFS(1 , 0);
    int maxnr = - INF;
    for(i = 1;i <= n; ++i){
        maxnr = max(maxnr , d[i]);
    }
    printf("%d\n",maxnr);
    return 0;
}