Program asmax;

const 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.