program chiralindex
      parameter (nat0=4000)
      dimension r(nat0,3),w(nat0)

      open(4,file='FILE.X')
      read(4,*)
      read(4,*)nat
      if(nat.gt.nat0)then
       write(6,*)'too many atoms'
       stop
      endif
      do 1 i=1,nat
1     read(4,*)idum,(r(i,ix),ix=1,3)
      close(4)

      write(6,600)nat
600   format(i5,' atoms, which is central? ',$)
      read(5,*)ic
      open(40,file='WEIGHT.LST')
      write(40,*)nat
      xc=r(ic,1)
      yc=r(ic,2)
      zc=r(ic,3)
      do 2 i=1,nat
      d=sqrt((xc-r(i,1))**2+(yc-r(i,2))**2+(zc-r(i,3))**2)
2     w(i)=1.0/(1.+d)
      write(40,400)(w(i),i=1,nat)
400   format(f10.6,' ',$)
      close(40)
      stop
      end