L+N-2L+N-3L+N-4L+N-5L+N-6L+N-7L+N-8L+N-9L+N-10L+N-11L+N-12L+N-13L+N-14L+N-15L+N-16L+N-17L+N-18L+N-19L+N-20L+N-21