410121: GYM103960 A Finding Maximal Non-Trivial Monotones

In this problem we will be dealing with character sequences, often called strings. A sequence is non-trivial if it contains at least two elements.

Given a sequence $$$s$$$, we say that a chunk $$$s_i, \ldots, s_j$$$ is monotone if all its characters are equal, and we say that it is maximal if this chunk cannot be extended to left or right without losing the monotonicity.

Given a sequence composed only of characters "a" and "b", determine how many characters "a" occur in non-trivial maximal monotone chunks.

The input consists of two lines. The first line contains a single integer $$$N$$$, where $$$1 \leq N \leq 10^5$$$. The second line contains a string with exactly $$$N$$$ characters, composed only of the characters "a" and "b".

Print a single line containing an integer representing the total number of times the character "a" occurs in non-trivial maximal monotone chunks.

7
abababa

0

7
bababab

0

10
aababaaabb

5

10
bbaababaaa

5