if ((p = 0) and (n = 0)) and ((Pc = 1) and (Nc = 1)) then
  writeln('undefined');

if (((p = 0) and (n <> 0)) or ((p <> 0) and (n = 0)))and ((Pc = 1) and (Nc = 1)) then
  writeln('error');

this pair if we have on input n and p (Nc = 1 and Pc = 1)
but still i have wa on 6 test!
are there any conditions for "error" and "undefined"??? please help. i've already sent my solution for 13 times! and still it's wa...

Oh, I have the same problem:(