DECLARE SUB PER (K)

OPEN "INPUT.TXT" FOR INPUT AS #1
OPEN "OUTPUT.TXT" FOR OUTPUT AS #2

INPUT #1, N
DIM B(31) AS INTEGER
DIM A(N, -1 TO 31) AS INTEGER

FOR I = 1 TO 31
B(I) = 1
NEXT I

MIN = 50
I = 1
DO UNTIL EOF(1)

INPUT #1, H
IF H = 0 THEN
  I = I + 1
ELSE
  A(I, H) = 1
END IF
LOOP

CALL PER(1)


D$ = ""
FOR I = 1 TO N
IF A(I, -1) <> 0 THEN D$ = D$ + STR$(A(I, -1))
NEXT I


IF D$ = "" THEN PRINT #2, "-1" ELSE D$ = RIGHT$(D$, LEN(D$) - 1): PRINT #2, D$

CLOSE #1, #2
SYSTEM

SUB PER (K)
SHARED A() AS INTEGER, B() AS INTEGER
SHARED N, MIN


FOR I = 1 TO 31

IF MIN < 50 THEN GOTO 5
IF A(K, I) = 1 THEN
  IF B(I) = 1 THEN
    B(I) = -1
    A(K, 0) = I
'    PRINT A(K, 0)
'    SLEEP
    IF K < N THEN
      CALL PER(K + 1)
    ELSE
      MAX = 0
      FOR L = 1 TO 31
        IF B(L) = -1 AND L > MAX THEN MAX = L
      NEXT L
      IF MAX < MIN THEN
        MIN = MAX
'        PRINT MAX, MIN
'        SLEEP
        FOR G = 1 TO K
          A(G, -1) = A(G, 0)
        NEXT G
        GOTO 5
      END IF
    END IF
   
    A(K, 0) = 0
    B(I) = 1
  END IF
END IF


NEXT I

5
END SUB