OPEN "input.txt" FOR INPUT AS #1
INPUT #1, N
DO WHILE NOT EOF(1)
LINE INPUT #1, S$
K = LEN(S$)
FOR A = 1 TO K STEP 2
m(i) = VAL(MID$(S$, A, 1))
PRINT m(i)
i = i + 1
NEXT A
LOOP
CLOSE #1
i = i - 1
FOR T = 1 TO i
 A = m(T)
 FOR X = (T + 1) TO i
  IF m(X) = A THEN m(X) = 0
 NEXT X
NEXT T
P = 0
FOR T = 1 TO i
 A = m(T)
 IF A <> 0 THEN P = P + 1
NEXT T
IF P < N THEN
 OPEN "OUTPUT.TXT" FOR OUTPUT AS #2
 PRINT #2, "-1"
 CLOSE #2
 SYSTEM
END IF
OPEN "OUTPUT.TXT" FOR OUTPUT AS #3
FOR T = 1 TO i
IF m(T) <> O THEN
PRINT #3, m(T);
END IF
NEXT T
CLOSE #3
SYSTEM