c---------------------------------------------------------------------
c                         PROGRAM RENUM          ECMeng   09/08
c  --interactive input/output specification
c  --sets chain IDs A,B,... for models delimited with MODEL/ENDMDL
c  --removes MODEL/ENDMDL lines
C  --also increments chain ID upon hitting TER, MODELs can have >1 chn
c  --does not renumber the atoms or residues
c---------------------------------------------------------------------
c
      character*80 pdblin, pdbfil, pdbout
      character*26 cids
      character*1 chainid
      integer atoms,count
c
      cids = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
c
      write (6, *) 'enter name of pdb input file:'
      read (5, 1000) pdbfil
 1000 format (A80)
      write (6, 1000) pdbfil
      write (6, *) 'enter name of output file:'
      read (5, 1000) pdbout
      write (6, 1000) pdbout
      open (unit=1, file=pdbfil, status='old')
      open (unit=2, file=pdbout, status='unknown')
c
      count = 1
      chainid = cids(1:1)
      atoms = 0
   50 read (1, 1000, end=500) pdblin
      if (pdblin(1:3).eq.'TER'.and.atoms.ne.0) then
        write (6,*) 'found TER, end of chain ',chainid
        count = count + 1
        chainid = cids(count:count)
        atoms = 0
        write (2,1002) 'TER'
 1002   format (a3)
      else if (pdblin(1:6).eq.'ENDMDL'.and.atoms.ne.0) then
        write (6,*) 'found ENDMDL, end of chain ',chainid
        count = count + 1
        chainid = cids(count:count)
        atoms = 0
      else if (pdblin(1:4).eq.'ATOM'.or.pdblin(1:4).eq.'HETA') then
        atoms = atoms + 1
        write (2,1001) pdblin(1:21),chainid,pdblin(23:80)
 1001   format (a21,a1,a58)
      endif
      go to 50
  500 continue
      close (1)
      close (2)
      end
c---------------------------------------------------------------------