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