IDENTIFICATION DIVISION.
       PROGRAM-ID. D1.

       ENVIRONMENT DIVISION.
       INPUT-OUTPUT SECTION.
       FILE-CONTROL.
           SELECT INPUT-FILE ASSIGN TO "INPUT1.TXT"
               ORGANIZATION IS LINE SEQUENTIAL.

       DATA DIVISION.
       FILE SECTION.
       FD INPUT-FILE.
       01 INPUT-LINE.
         05 LEFT-NO  PIC 9(5).
         05 FILLER   PIC X(3).
         05 RIGHT-NO PIC 9(5).

       WORKING-STORAGE SECTION.
       01 LEFT-NOS OCCURS 1000 INDEXED BY LEFT-IDX.
           05 LEFT-NO-ELT PIC 9(5).
       01 RIGHT-NOS OCCURS 1000 INDEXED BY RIGHT-IDX.
           05 RIGHT-NO-ELT PIC 9(5).
       01 IDX PIC 9(5).
       01 ANSWER PIC 9(9).
       01 EOF PIC X VALUE "N".

       PROCEDURE DIVISION.
           OPEN INPUT INPUT-FILE.
           PERFORM READ-LINE UNTIL EOF = "Y".
           PERFORM SORT-TABLES.
           PERFORM PART-1.
           DISPLAY ANSWER.
           CLOSE INPUT-FILE.
           STOP RUN.

       READ-LINE.
           READ INPUT-FILE
               AT END MOVE "Y" TO EOF
               NOT AT END PERFORM PARSE-LINE
           END-READ.

       PARSE-LINE.
           MOVE LEFT-NO TO LEFT-NOS(LEFT-IDX).
           MOVE RIGHT-NO TO RIGHT-NOS(RIGHT-IDX).
           ADD 1 TO LEFT-IDX RIGHT-IDX.

       SORT-TABLES.
           SORT LEFT-NOS ON ASCENDING KEY LEFT-NO-ELT.
           SORT RIGHT-NOS ON ASCENDING KEY RIGHT-NO-ELT.

       PART-1.
           PERFORM VARYING IDX FROM 1 BY 1 UNTIL IDX > 1000
               COMPUTE ANSWER =
                   ANSWER +
                   FUNCTION ABS(LEFT-NO-ELT(IDX) - RIGHT-NO-ELT(IDX))
               END-PERFORM.

       DBG-TBLS.
           PERFORM VARYING IDX FROM 1 BY 1 UNTIL IDX > 1000
               DISPLAY 'LEFT: ' LEFT-NOS(IDX) ', RIGHT: ' RIGHT-NOS(IDX)
           END-PERFORM.