My code:

type graph=^node;
    node=record v:longint;next:graph;end;
var g:array[1..6000] of graph;
    f:array[1..6000,0..1] of longint;
    a,deg:array[1..6000] of longint;
    n:longint;
function max(a,b:longint):longint;
begin
    if a<b then exit(b) else exit(a);
end;
procedure init;
var i,x,y:longint;
    p:graph;
begin
    read(n);
    for i:=1 to n do read(a[i]);
    repeat
     read(x,y);
     if (x<>0) or (y<>0) then
      begin
      new(p);inc(deg[x]);
      p^.v:=x;p^.next:=g[y];g[y]:=p;
      end;
    until (x=0) and (y=0);
    fillchar(f,sizeof(f),0);
end;
function search(v,x:longint):longint;
var p:graph;
    i:longint;
begin
        if f[v,x]<>0 then exit(f[v,x]);
        if x=1 then f[v,x]:=a[v];
        p:=g[v];
    if x=0 then
          begin
          while p<>nil do
            begin
            f[v,x]:=f[v,x]+max(search(p^.v,0),search(p^.v,1));
            p:=p^.next;
            end;
          end
        else begin
             while p<>nil do
               begin
               f[v,x]:=f[v,x]+search(p^.v,0);
               p:=p^.next;
               end;
             end;
        exit(f[v,x]);
end;
procedure work;
var i,j,c,ans,k:longint;
begin
        ans:=0;
    for i:=1 to n do
      if deg[i]=0 then
             inc(ans,max(search(i,0),search(i,1)));
        writeln(ans);
end;
begin
    init;
    work;
end.

{$M 16777216}