A. Finding Maximal Non-Trivial Monotones
time limit per test
0.25 seconds
memory limit per test
1024 megabytes
input
standard input
output
standard output

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.

Input

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".

Output

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

Examples
Input
7
abababa
Output
0
Input
7
bababab
Output
0
Input
10
aababaaabb
Output
5
Input
10
bbaababaaa
Output
5