parameter n1=500,n2=500
	real tv(n1,n2),tu(n1,n2),rho(n1,n2),
     *  ex(n1,n2),ey(n1,n2),e(n1,n2)
	open(20,file='potent.dat')
	open(30,file='electr.dat')
	read *,nt
	
	do i=1,n1
	do j=1,n2
	tv(i,j)=0.
	tu(i,j)=0.
	enddo
	enddo
	
	do i=100,400
	rho(i,200)=-1.
	rho(i,250)=+1.
	enddo
	
	do k=1,nt
	
	do i=2,n1-1
	do j=2,n2-1
	tu(i,j)=tv(i,j)-rho(i,j)+
     *	0.05*((tv(i+1,j)+tv(i-1,j)-2.*tv(i,j))+
     *	(tv(i,j+1)+tv(i,j-1)-2.*tv(i,j)))	
	enddo
	enddo
	
	do i=1,n1
	do j=1,n2
	tv(i,j)=tu(i,j)
	enddo
	enddo
	
	enddo
	
	do i=2,n2-1
	do j=2,n1-1
	ex(i,j)=tv(i+1,j)-tv(i-1,j)
	ey(i,j)=tv(i,j+1)-tv(i,j-1)
	e(i,j)=sqrt(ex(i,j)**2+ey(i,j)**2)
	enddo
	enddo
100	format (500 e15.6)
	write (20,100) tu
	write (30,100) e

	stop
	end