external func
        a=0.
        b=1.
        abserr=0.0000
        relerr=0.0000001
        call  quanc8(func,a,b,abserr,relerr,result,errest,nofun,flag)
	print *,result*4.,errest
	stop
	end
	function func(x)
	func=sqrt(abs(1.-x*x))
	return
	end