Description

There is a string composed only of 0s and 1s. For a given substring, if swapping 0s and 1s and then reversing it results in the same original substring, then the substring is considered "anti-symmetric." Given a string of length N, how many substrings are "anti-symmetric"?

Input Format

The first line contains a positive integer N (0 ≤ N ≤ 10000).

The second line contains a 01 string of length N.

Output Format

Output the number of "anti-symmetric" substrings.

8
11001011

7

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