100 CLS : REM  10 HOME for Applesoft BASIC
110 DIM D(100)
120 FOR P = 1 TO 100
130   FOR T = P TO 100 STEP P
140     D(T) = NOT D(T)
150   NEXT T
160 NEXT P
170 ' Print "opened" doors
180 FOR I = 1 TO 100
190   IF D(I) THEN PRINT I;" ";
200 NEXT I
210 END