You are given a playlist of a radio station since its establishment. The playlist has a total of $n$ songs.
What is the longest sequence of successive songs where each song is unique?
The first input line contains an integer $n$ : the number of songs.
The next line has $n$ integers $k_1,k_2,\ldots,k_n$ : the id number of each song.
Print the length of the longest sequence of unique songs.