const f = 'asmax.in'; g = 'asmax.out';

type pnod = ^nod;
     nod = record
        next : pnod;
        info : longint;
end;

var
    a : array[0..16001] of pnod;
    c : array[0..16001] of longint;
    viz : array[0..16001] of byte;
    x, y, n : longint;
    s, max, i : longint;
    p : pnod;
    buf, buf1 : array[1..1 shl 17] of char;

procedure add( var dest : pnod; val : longint );
    var
        q : pnod;

    begin
        new( q );
        q^.info := val;
        q^.next := dest;
        dest := q;
    end;

procedure dfs( nod : longint );
    var
        q : pnod;

    begin
        viz[nod] := 1;
        q := a[nod];
        while q <> nil do begin
            if viz[q^.info] = 0 then
            begin
                dfs( q^.info ) ;
                if (c[q^.info] > 0) then c[nod] := c[nod] + c[q^.info];
            end;
            q := q^.next;
        end;
    end;
begin
    assign( input,f ); reset( input );
    assign( output,g ); rewrite( output );
    settextbuf( input,buf );
    settextbuf( output,buf1 );
    readln(n );
    for i := 1 to n do read(c[i]);
    for i:=1 to n-1 do begin
        readln(x, y);
        add( a[x], y );
        add( a[y], x );
    end;
    max := -200000000;
    dfs(1);
    for i := 1 to n do if c[i] > max then max := c[i];
    writeln( max );
end.