using namespace std;
#include<iostream>
#include<stdio.h>
FILE *f,*g;
int s[16001],w[2][49999],start[16001],n,c[16001],s1[16001],ic=1,sf=1;
int mx=-9999999,h,mx1=-9999999;
void df(int nod)
{   int t;
    s1[nod]=1;
    t=start[nod];
    while(t)
    {
        if(s1[w[0][t]]==0)
                df(w[0][t]);

        if(w[1][t]==0&&s[w[0][t]]!=-9999999)
        {
            if(s[nod]>=0)
                    if(h==0)
                    {s[w[0][t]]+=s[nod];s[nod]=-9999999;}
                     else
                        if(h==1&&s[w[0][t]]+s[nod]>=0)
                     {s[w[0][t]]+=s[nod];cout<<endl<<w[0][t]<<"    "<<nod<<"   sum="<<s[w[0][t]];
                         s[nod]=-9999999;}
            if(mx<s[w[0][t]]) mx=s[w[0][t]];
        }
        t=w[1][t];

    }


}
int main()
{
    int i=0,x=0,y=0,j=0,t=0;
    f=fopen("asmax.in","r");
    g=fopen("asmax.out","w");
    fscanf(f,"%d",&n);
    for(i=1;i<=n;i++)
        {fscanf(f,"%d",&s[i]);
        if(mx1<s[i]) {mx1=s[i];j=i;}
        }
        if(mx1>0) h=1;
    t=0;
    for(i=1;i<n;i++)
    {
        fscanf(f,"%d %d",&x,&y);
        t++;w[0][t]=y;w[1][t]=start[x];
        start[x]=t;
        t++;w[0][t]=x;
        w[1][t]=start[y];
        start[y]=t;

    }
df(1);
if(mx>mx1)
fprintf(g,"%d",mx);
else fprintf(g,"%d",mx1);
}