program aveg
      implicit none
      integer*4 n0
      parameter (n0=2000)
      integer*4 it(n0),ig,i,nat,ix
      real*8 x(3),a(n0,3)

      write(6,*)' Makes average geometry from geometries in FILE.X'
      open(9,file='FILE.X')
      ig=0

1     read(9,*,end=99,err=99)
      read(9,*,end=99,err=99)nat
      if(nat.gt.n0)call report('too many atoms')
      ig=ig+1
      if(ig.eq.1)then
       write(6,*)nat,' atoms'
       do 4 i=1,nat
 4     a(i,ix)=0.0d0
      endif
      do 3 i=1,nat
      read(9,*)it(i),(x(ix),ix=1,3)
      do 3 ix=1,3
3     a(i,ix)=a(i,ix)+x(ix)
      goto 1
99    close(9)
      write(6,*)ig,' geometries'

      if(ig.eq.0)stop

      do 5 i=1,nat
      do 5 ix=1,3
5     a(i,ix)=a(i,ix)/dble(ig)

      open(9,file='AVE.X')
      write(9,*)'average geometry from ',ig
      write(9,*)nat
      do 2 i=1,nat
2     write(9,900)it(i),(a(i,ix),ix=1,3)
900   format(i6,3f12.6)
      close(9)   
      stop
      end
      subroutine report(o)
      character*(*) o
      write(6,*)o
      stop
      end