Advent of Code 2020, problem 1.1 in Cobol

aoc1.cbl

IDENTIFICATION DIVISION.
PROGRAM-ID. AOC1.

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

DATA DIVISION.
   FILE SECTION.
   FD INPUTFILE.
   01 DIGIT PIC 9(4).

   WORKING-STORAGE SECTION.
   01 WS-DIGIT PIC 9(4).
   01 WS-EOF PIC A(1).
   01 WS-TABLE.
      05 WS-A PIC A(1) OCCURS 2020 TIMES VALUE 'N'.
   01 WS-OUTCOME PIC 9(8).
   01 WS-OTHER PIC 9(4).

PROCEDURE DIVISION.
   OPEN INPUT INPUTFILE.
      PERFORM UNTIL WS-EOF='Y'
         READ INPUTFILE INTO WS-DIGIT
            AT END MOVE 'Y' TO WS-EOF
            NOT AT END PERFORM PROCESS-NUMBER
         END-READ
      END-PERFORM.
   CLOSE INPUTFILE.
   STOP RUN.

PROCESS-NUMBER.
   MOVE 'Y' TO WS-A(WS-DIGIT).
   SUBTRACT WS-DIGIT FROM 2020 GIVING WS-OTHER.
   IF WS-A(WS-OTHER)='Y'
      MULTIPLY WS-DIGIT BY WS-OTHER GIVING WS-OUTCOME
      DISPLAY WS-OUTCOME
   END-IF.