CF846A Curriculum Vitae

Hideo Kojima has just quit his job at Konami. Now he is going to find a new place to work. Despite being such a well-known person, he still needs a CV to apply for a job. During all his career Hideo has produced $ n $ games. Some of them were successful, some were not. Hideo wants to remove several of them (possibly zero) from his CV to make a better impression on employers. As a result there should be no unsuccessful game which comes right after successful one in his CV. More formally, you are given an array $ s_{1},s_{2},...,s_{n} $ of zeros and ones. Zero corresponds to an unsuccessful game, one — to a successful one. Games are given in order they were produced, and Hideo can't swap these values. He should remove some elements from this array in such a way that no zero comes right after one. Besides that, Hideo still wants to mention as much games in his CV as possible. Help this genius of a man determine the maximum number of games he can leave in his CV.

The first line contains one integer number $ n $ ( $ 1

Print one integer — the maximum number of games Hideo can leave in his CV so that no unsuccessful game comes after a successful one.