real y(4),work(27)
	integer iwork(5)
	common  alpha,q,s
	external f
	open (10,file='ruth.in')
	open (20, file='ruth.out')
	neqn=4
	read(10,*)dt,nt,relerr,abserr,s,q,alpha,y
		
	talg=0
	tlopp=0
	iflag=1
	call rkf45(f,neqn,y,talg,tlopp,relerr,abserr,iflag,work,iwork)

	do i =1,nt
	tlopp=talg+dt
	iflag=2
	call rkf45(f,neqn,y,talg,tlopp,relerr,abserr,iflag,work,iwork)
	talg=tlopp
	write(20,100)y(1:2)
100	format(6f15.5)
	enddo
	stop
	end
	
	subroutine f(t,y,dy)
	real y(4),dy(4)
	common  alpha,q,s
	dy(1)=y(3)
	dy(2)=y(4)
	r=sqrt((y(1)-s)**2+y(2)**2)
	dy(3)=q*alpha*(y(1)-s)/r**3
	dy(4)=q*alpha*y(2)/r**3
	return
	end