program read_n_find_max_min
      character*20 fname
      write(*,*)'Which file to read data?(20 chr)'
      read(*,*) fname
      open(unit=12,file=fname)
      read(12,*)n
      write(*,*)'There are',n,'data points in your file.'
      read(12,*)a
      a_max = a
      a_min = a
      do i=2,n
        read(12,*)a
        if(a > a_max) a_max = a
        if(a < a_min) a_min = a
      end do
      write(*,*)'The maximum is :',a_max
      write(*,*)'The minimum is :',a_min
      close(12)
      end