just put all the numbers in a array of boolean.

var
  n,i,caint:longint;
  b:array[-100000..100000]of boolean;
begin
  readln(n);
  fillchar(b,sizeof(b),false);
  for i := 1 to n do
    begin
      readln(caint);
      b[caint]:=true;
    end;
  readln(n);
  for i := 1 to n do
    begin
      readln(caint);
      if b[10000-caint] then
        begin
          writeln('YES');
          halt;
        end;
    end;
  writeln('NO');
end.

Edited by author 10.09.2009 08:34