program dynamic_array
  implicit none
  integer, allocatable, dimension (:,:) :: a
  integer :: m, n, i, j

  print *, 'Give matrix dimensions ( rows, columns):'
  read *, m, n
  print '(2(a,i2))', 'm=', m, '  n=', n
  allocate (a(m,n))
  do j = 1, n
    do i = 1, m
      a(i,j) = (i-1)*n + j
    end do
  end do
  do i = 1, m
    print *, a(i,:)
  end do
  deallocate (a)
end program dynamic_array