0 GRAPHICS 1:COLOR 10:C=9:GOTO 2
1 PLOT X,C+A:DRAWTO X,C+B:PLOT X,C-A:DRAWTO X,C-B:RETURN
2 READ A,B:GOSUB 1:X=16-X:GOSUB 1:X=17-X:IF X<9 THEN 2
3 DATA 4,4,3,4,2,4,1,4,0,8,0,7,0,6,0,5,0,4
