CF899B Months and Years

Everybody in Russia uses Gregorian calendar. In this calendar there are $ 31 $ days in January, $ 28 $ or $ 29 $ days in February (depending on whether the year is leap or not), $ 31 $ days in March, $ 30 $ days in April, $ 31 $ days in May, $ 30 $ in June, $ 31 $ in July, $ 31 $ in August, $ 30 $ in September, $ 31 $ in October, $ 30 $ in November, $ 31 $ in December. A year is leap in one of two cases: either its number is divisible by $ 4 $ , but not divisible by $ 100 $ , or is divisible by $ 400 $ . For example, the following years are leap: $ 2000 $ , $ 2004 $ , but years $ 1900 $ and $ 2018 $ are not leap. In this problem you are given $ n $ ( $ 1

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In the first example the integers can denote months July, August, September and October. In the second example the answer is no, because there are no two consecutive months each having $ 30 $ days. In the third example the months are: February (leap year) — March — April – May — June. In the fourth example the number of days in the second month is $ 28 $ , so this is February. March follows February and has $ 31 $ days, but not $ 30 $ , so the answer is NO. In the fifth example the months are: December — January — February (non-leap year).