subroutine mascnv (im1, im2)
c
c----------------------------------------------------------------------
c Routine converts mass settings which may have been expressed in
c lower mass detector nomenclature into high mass detector settings.
c----------------------------------------------------------------------
c
      if (im1 .gt. 0  .and.  im2. gt. 0) return
      jm1 = -im1 / 4
      jm2 = -im2 / 4
      im1 = min0(jm1, jm2)
      im2 = max0(jm1, jm2)
c
c----------------------------------------------------------------------
c----------------------------------------------------------------------
c
      return
      end