10 D=100: DIMD(D): P=1
20 PRINT CHR$(147);"PASS: ";P
22 FOR I=P TO D STEP P: D(I)=NOTD(I): NEXT
30 IF P=100 THEN 40
32 P=P+1: GOTO20
40 PRINT: PRINT"THE FOLLOWING DOORS ARE OPEN: "
42 FOR I=1 TO D: IF D(I)=-1 THEN PRINTI;
44 NEXT