DEFINE MAXSIZE="1000"
CARD ARRAY stack(MAXSIZE)
CARD stacksize=[0]

BYTE FUNC IsEmpty()
  IF stacksize=0 THEN
    RETURN (1)
  FI
RETURN (0)

PROC Push(BYTE v)
  IF stacksize=maxsize THEN
    PrintE("Error: stack is full!")
    Break()
  FI
  stack(stacksize)=v
  stacksize==+1
RETURN

BYTE FUNC Pop()
  IF IsEmpty() THEN
    PrintE("Error: stack is empty!")
    Break()
  FI
  stacksize==-1
RETURN (stack(stacksize))

CARD FUNC Ackermann(CARD m,n)
  Push(m)
  WHILE IsEmpty()=0
  DO
    m=Pop()
    IF m=0 THEN
      n==+1
    ELSEIF n=0 THEN
      n=1
      Push(m-1)
    ELSE
      n==-1
      Push(m-1)
      Push(m)
    FI
  OD
RETURN (n)

PROC Main()
  CARD m,n,res

  FOR m=0 TO 3
  DO
    FOR n=0 TO 4
    DO
      res=Ackermann(m,n)
      PrintF("Ack(%U,%U)=%U%E",m,n,res)
    OD
  OD
RETURN