subroutine indexx(n,arr,indx)
parameter (NMAX=3000)
integer indx(n)
real arr(n)
real brr(NMAX)
if(n.gt.NMAX) then
print*,'n=',n,' too big in indexx.'
stop
endif
do i=1,n
brr(i)=arr(i)
indx(i)=i
enddo
call ssort(brr,indx,n,2)
return
end