program specaven1n2
c     average of N1...N2 spectra from SP.LST
      implicit none
      integer ns,np,i,ii,is,ie,n1,n2
      real*8,allocatable::sx(:),sa(:)
      real*8 sy,x,y
      character*80 s80

      call getarg(1,s80)
      read(s80,*)n1
      call getarg(2,s80)
      read(s80,*)n2
      
      ns=0
      ii=0
      open(9,file='SP.LST')
992   read(9,900,end=918,err=918)s80
900   format(a80)
      ns=ns+1
      if(ns.eq.1)then
       open(10,file=s80)
       np=0
993    read(10,*,end=919,err=919)x,y
       np=np+1
       goto 993
919    close(10)
       allocate(sx(np),sa(np))
       do 4 i=1,np
4      sa(i)=0.0d0
      endif
      if(ns.le.n2.and.ns.ge.n1)then
       open(10,file=s80)
       do 1 i=1,np
       read(10,*)sx(i),sy
1      sa(i)=sa(i)+sy
       close(10)
       ii=ii+1
      endif
      goto 992
918   close(9)
      do 2 i=1,np
2     sa(i)=sa(i)/dble(ii)
      write(s80,'(i80)')ii
      do 5 is=1,len(s80)
5     if(s80(is:is).ne.' ')goto 6
6     do 7 ie=len(s80),1,-1
7     if(s80(ie:ie).ne.' ')goto 8
8     open(10,file='AVE.PRN')
      do 3 i=1,np
3     write(10,100)sx(i),sa(i)
100   format(f10.4,' ',g12.6)
      close(10)
      write(6,6000)ns,ii,np
6000  format(i5,' spectra in SP.LST',/,
     1       i5,' spectra averaged in AVE.PRN ',/,
     1       i5,' points')
      end