program ese
      implicit none
      integer i,j,nat
      real*8 e,d,bohr
      real*8 ,allocatable::r(:,:),z(:)
      bohr=0.529177249d0
      open(9,file='FILE.X')
      read(9,*)
      read(9,*)nat
      allocate(z(nat),r(nat,3))
      do 1 i=1,nat
 1    read(9,*)z(i),(r(i,j),j=1,3)
      close(9)
      r=r/bohr
      e=0.0d0
      do 3 i=1,nat
      do 3 j=i+1,nat
      d=sqrt((r(i,1)-r(j,1))**2+(r(i,2)-r(j,2))**2+(r(i,3)-r(j,3))**2)
 3    e=e+z(i)*z(j)/d
      write(6,60)e
 60   format(F19.9)
      end