; r0 - state
start:
    mov r0, 0
wait:
    jb p1.1, maybe_n
    jb p2.1, maybe_d
maybe_n:
    lcall delay
    jb p1.1, n
    jmp wait
maybe_d:
    lcall delay
    jb p2.1, d
    jmp wait
n:
    inc r0
    jmp check
d:
    inc r0
    inc r0
check:
    mov a, r0
    sub a, 3
    jnc done
    jmp wait
done:
    ; open door here
    jmp start