C_______________________________________________________________________________
C    Subrutina Alterar, de dificil comprension y cuyo objetivo se desconoce
C_______________________________________________________________________________

      Subroutine Alterar(n,v)
      implicit real*8 (a-h,o-z)
      dimension v(n)

      i=1
    1 j=n
    2   if (v(i).le.v(j)) goto 3
          vc  =v(i)
          v(i)=v(j)
          v(j)=vc
    3     j=j-1
        if(j.gt.i) goto 2
        i=i+1
      if (i.lt.n) goto 1
 
      return
      end
