#include <iostream>

#include <fstream>

const int MAXN=16000;

filein='asmax.in';

fileout='asmax.out';

type longarray=array[1.MAXN] of longint;

plongarray=^longarray;

plist=^list;

list=record

     next:
     integer;

urm:
plist;

end;

var edge:
array[1.MAXN] of plist;

v,max,tata:
plongarray;

n:
integer;

procedure readinput;

var i,j,k:
integer;

aux:
plist;

begin

assign(input,filein);

reset(input);

read(n);

new(v);

for i:
    =1 to n do

         begin

         read(v^[i]);

edge[i]:
    =nil;

end;

for k:
    =1 to n-1 do

         begin

         read(i,j);

new(aux);

aux^.next:
    =j;

aux^.urm:
    =edge[i];

edge[i]:
    =aux;

new(aux);

aux^.next:
    =i;

aux^.urm:
    =edge[j];

edge[j]:
    =aux;

end;

close(input);

end;

procedure compute(nod:integer);

var aa:
plist;

i:
integer;

begin

max^[nod]:
    =v^[nod];

aa:
    =edge[nod];

while (aa<>nil) do

        begin

i:
            =aa^.next;

if (i<>tata^[nod]) then

    begin

tata^[i]:
        =nod;

compute(i);

if (max^[i]>0) then

max^[nod]:
        =max^[nod]+max^[i];

end;

aa:
    =aa^.urm;

end;

end;

procedure print;

var maxim:
longint;

i:
integer;

begin

maxim:
    =max^[1];

for i:
    =2 to n do

         if (max^[i]>maxim) then

     maxim:
                 =max^[i];

assign(output,fileout);

rewrite(output);

writeln(maxim);

close(output);

end;

begin

readinput;

new(tata);

fillchar(tata^,sizeof(longarray),0);

new(max);

fillchar(max^,sizeof(longarray),0);

compute(1);

print;

end.