Discussion on: Advent of Code 2020 Solution Megathread - Day 5: Binary Boarding

   IDENTIFICATION DIVISION.
   PROGRAM-ID. AOC-2020-05-1.
   AUTHOR. ANNA KOSIERADZKA.

   ENVIRONMENT DIVISION.
   INPUT-OUTPUT SECTION.
   FILE-CONTROL.
       SELECT INPUTFILE ASSIGN TO "d5.input"
       ORGANIZATION IS LINE SEQUENTIAL.

   DATA DIVISION.
   FILE SECTION.
     FD INPUTFILE.
     01 INPUTRECORD PIC X(10).
   WORKING-STORAGE SECTION.
     01 FILE-STATUS PIC 9 VALUE 0.

   LOCAL-STORAGE SECTION.
     01 I UNSIGNED-INT VALUE 1.
     01 SEAT-ID UNSIGNED-INT VALUE 0.
     01 ID-MAX UNSIGNED-INT VALUE 0.

   PROCEDURE DIVISION.
   001-MAIN.
       OPEN INPUT INPUTFILE.
       PERFORM 002-READ UNTIL FILE-STATUS = 1.
       CLOSE INPUTFILE.
       DISPLAY ID-MAX.
       STOP RUN.

   002-READ.
        READ INPUTFILE
            AT END MOVE 1 TO FILE-STATUS
            NOT AT END PERFORM 003-PROCESS-RECORD
        END-READ.

   003-PROCESS-RECORD.
       MOVE 0 TO SEAT-ID. 
       PERFORM VARYING I FROM 1 BY 1 UNTIL I > 10
          COMPUTE SEAT-ID = SEAT-ID * 2
          IF INPUTRECORD(I:1) = 'B' OR INPUTRECORD(I:1) = 'R' THEN 
             ADD 1 TO SEAT-ID
          END-IF
       END-PERFORM.

       IF SEAT-ID > ID-MAX THEN
         MOVE SEAT-ID TO ID-MAX
       END-IF.