Mouse Basic program needs correction

This program needs corrections to operate properly. Your input please...

1 REM **********************

2 REM * MOUSE SKETCH *

3 REM **********************

100 REM *** VARIABLE USAGE ***

110 REM * X, Y = CURRENT MOUSE POSITION

120 REM * OX, OY = PREVIOUS POSITION

130 REM * C = COLOR AT (X,Y)

140 REM * S = MOUSE BUTTON STATUS

150 REM * N = MOUSE SLOT NUMBER

200 GOSUB 710: IF N = 0 THEN PRINT "NO MOUSE DETECTED!": END

210 GOSUB 620: REM INITIALIZE SCREEN & MOUSE

220 PRINT D$"IN#"N: REM GET INPUT FROM MOUSE

230 REM *** MAIN LOOP ***

240 GOSUB 390: REM READ MOUSE POSITION

250 GOSUB 300: REM UPDATE SCREEN

260 GOTO 230 : REM LOOP

300 REM *** SCREEN UPDATE LOGIC ***

310 IF PEEK (49249) >= 128 OR PEEK (49250) >= 128 THEN IF S < 3 THEN C = 0: COLOR=0: GOTO 330

320 IF OX <> X OR OY <> Y THEN IF S >= 2 THEN COLOR = C: PLOT OX,OY: C = SCRN(X,Y)

330 IF S < 0 THEN GOSUB 460: RETURN

340 COLOR = 15: IF S > 2 THEN COLOR = 1

350 PLOT X, Y

360 OX = X: OY = Y

370 RETURN

390 REM *** GET MOUSE DATA ***

400 INPUT "";X,Y,S

410 X = INT (X / 25.575)

420 Y = INT (Y / 25.575)

430 RETURN

460 REM *** HANDLE KEYBOARD INPUT ***

470 POKE -16368,0

480 PRINT D$"IN#0"

490 PRINT "RETURN=CONTINUE, ESC=QUIT, CTRL-C=CLEAR";: GET A$

500 IF A$ = CHR$(3) THEN HOME: GOSUB 620: RETURN

510 IF A$ = CHR$(13) THEN RETURN

520 IF A$ = CHR$(27) THEN END

530 PRINT CHR$(7): GOTO 490

600 REM *** INITIALIZE SCREEN & MOUSE ***

610 HOME: GR

620 D$ = CHR$(4)

630 C = 0

640 PRINT D$"PR#"N: PRINT CHR$(1)

650 PRINT D$"PR#0"

660 RETURN

710 REM *** FIND MOUSE SLOT ***

720 FOR I = 1 TO 7

730 IF PEEK(49420 + 256 * (I - 1)) = 32 AND PEEK(49659 + 256 * (I - 1)) = 214 THEN N = I: RETURN

740 NEXT I

750 N = 0

760 RETURN