I'm having problems programming the mandelbrot set for my Ti-83 plus. I have double-checked that I entered it in correctly, but it keeps getting messed up. this is the program I'm using:

:3->dim(L1)

:3->dim(L2)

:FnOff

:AxesOff

:PlotsOff

:GridOff

:–2.31->Xmin

:.035->∆X

:–1.085->Ymin

:∆X->∆Y

:Input "STAGE(≥4):",K

:If K<4:4->K

:Disp "MOMENT PLEASE.."

:ClrDraw

:0->T:3->N

:0.24->L1(N)

:0->L2(N)

:

:Lbl F

:1->Z:Goto M

:

:Lbl 1

:If T=0:Then

:L1(N)+∆X->L1(N)

:Goto F

:End

:

:1->J:2->P

:L1(N)-∆X->L1(J)

:L1(N)->L1(P)

:L1(N)->L2(J)

:L2(N)->L2(P)

:L2(N)+∆Y->L2(N)

:Pt-On(L1(J),L2(J))

:

:L1(J)->U

:L2(J)->V

:L1(P)->W

:L2(P)->A

:

:2->Z

:

:Lbl S

:Goto M

:

:Lbl 2

:If T=0

:Then

:Pt-On(L1(N),L2(N))

:Pt-On(L1(N),–L2(N))

:J->R:N->J

:Else

:P->R:N->P

:End

:R->N

:L1(J)+L1(P)-L1(R)->L1(N)

:L2(J)+L2(P)-L2(R)->L2(N)

:If L2(N)≥0:Goto S

:

:Lbl Q

:Text(0,0,K)

:Stop

:

:Lbl M

:L1(N)->X

:L2(N)->Y

:0->T

:If X<Xmin or X>Xmax or Y<Ymin or Y>Ymax

:1->T

:1->I

:While I<K and T=0

:I+1->I

:X¯->Q:Y¯->S

:If Q+S>5

:Then

:1->T

:Else

:2XY+L2(N)->Y

:Q-S+L1(N)->X

:End

:End

:If Z=1:Goto 1

:If Z=2:Goto 2

The part I don't understand is the X¯ and Y¯, I couldn't enter that into my calculator so I used X and Y instead. If there's something I'm doing wrong then I don't see it. Any helpful advice would be appreciated.