 IDENTIFICATION DIVISION.
 PROGRAM-ID. TEST135.

 DATA DIVISION.
 WORKING-STORAGE SECTION.

  01 INP       PIC X(30).
  01 A         PIC 9(10).
  01 B         PIC 9(10).
  01 TTL       PIC 9(12).
  01 K         PIC ZZZZZZZZZ9.
  01 AMA       PIC 9(1).

 PROCEDURE DIVISION.
  ACCEPT INP.
  UNSTRING INP DELIMITED BY ' '
      INTO A B.

  COMPUTE TTL = A + B.  
  DIVIDE TTL BY 2 GIVING K REMAINDER AMA.

  IF AMA = 0
    DISPLAY K
  ELSE
    DISPLAY 'IMPOSSIBLE'
  END-IF.

 STOP RUN.