RosettaCodeData/Task/Fibonacci-sequence/PL-0/fibonacci-sequence.pl0

var n, a, b, i, tmp;
begin
  ? n;
  a := 0; b := 1;
  i := 2;
  while i <= n do
  begin
    tmp := b; b := a + b; a := tmp;
    i := i + 1
  end;
  ! b
end.