real w(-1:1)
        data w/1.,4.,1./
        write (*,*) 'Enter size dx:'
        read (*,*) d
        write (*,*) 'Enter x,y,z:'
        read (*,*) xc,yc,zc
        h=d/2.
        sum=0.
        do i=-1,1
        wx=w(i)
        x=i*h
        do j=-1,1
        wy=w(j)
        y=j*h
        do k=-1,1
        wz=w(k)
        z=k*h
        r=sqrt((x-xc)**2+(y-yc)**2+(z-zc)**2)
        sum=sum+wx*wy*wz/r
        enddo
        enddo
        enddo
        write (*,*) sum

        end