COMMON IGX1, IGX2
	DIMENSION IGX1(1600), IGX2(1600)
	ICX = 95
	ICY = 100
	CALL GSTART
10	READ(1,20) IR
20	FORMAT(I3)
	IF(IR)50,30,30
30	CALL GCLEAR
	IY1 = ICY - IR
	IY2 = ICY + IR
	DO 40 IY = IY1,IY2
	IYCY = IY - ICY
	ISQT = IFIX(0.5+SQRT(FLOAT(IR*IR-IYCY*IYCY)))
	IX1 = ICX - ISQT
	IX2 = ICX + ISQT
	CALL GPLOT(IX1,IY,0)
	CALL GPLOT(IX2,IY,1)
40	CONTINUE
	GO TO 10
50	CALL GSTOP
	STOP
	END