program readene
      implicit none
      INTEGER(4) i
      INTEGER(4) lbin,ibinit,kt,ibin,nmis
      REAL(8) ek,wk,ebin,ebin2,wbin,de
      
      write(6,*) 'lbin,ndrop'
      read(5,*) lbin,ibinit

      kt=0
      ibin=0

      ek=0.d0
      ebin=0.d0
      ebin2=0.d0
      wk=0.d0
      wbin=0.d0

      do while(kt.ge.0)
       kt=kt+1
       read(12,end=100) i,de
       ek=ek+de
       wk=wk+1.d0
       if(mod(kt,lbin).eq.0) then
        ibin=ibin+1
        if(ibin.ge.ibinit) then
         ebin=ebin+ek
         wbin=wbin+wk
         ebin2=ebin2+ek**2/wk
        endif
        write(20,*) ek,wk
        ek=0.d0
        wk=0.d0
       endif
      enddo

100   continue
      nmis=ibin-ibinit+1
      ebin=ebin/wbin
      ebin2=dsqrt(dabs(ebin2/wbin-ebin**2))
      ebin2=ebin2/dsqrt(dfloat(nmis))
      write(6,*) ' Independent bins ',nmis,'of lenght ',lbin
      write(6,*)
      write(6,*) ' Energy'
      write(6,*) ebin,ebin2
      write(6,*)

      stop
      end