It's a holiday season for all school students around the world! Unfortunately, Mahamba is busy preparing for International Olympiad in Informatics, which will be held in Tehran, Iran. He is now facing a new challenge from his teacher Aceka, and it goes something like this:

You have a string x of length N, which consists of small English letters. You have to find the number of indexes a, b, c and d, such that \(1 <= a < b < c < d <= N\) and \(x_a == x_c\), as well as \(x_b == x_d\).

He is baffled and definitely needs some help. So, you, the best programmer in Lalalandia, decided to give him a hand!

Input format

The first line contains the number N - the length of a string x. The second line contains the string x itself.

Output format

The first and only line should contain the answer to the problem.

Constraints

\(1 <= N <= 2000\)

The string x only contains small English letters.