parse arg n If n < 1 Then Do n = 1 End R = Ack(3,N) say "Ack(3,"n"): "R exit Ack: PROCEDURE PARSE ARG M,N IF M<1 THEN RETURN N+1 IF N<1 THEN RETURN Ack(M-1, 1) R1 = Ack(M, N-1) RETURN Ack(M-1, R1)