Given a string S consisting of N letters a and b. In one move you can replace one letter by the other (a by b or b by a).

Write a function solution that given such a string S, returns the minimum number of moves required to obtain a string containing no instances of three identical consecutive letters.

Output: 1

Explanation: The string without three identical consecutive letters which can be obtained is one move is "baabaa".

Output: 1

Explanation: The string without three identical consecutive letters which can be obtained is one move is "baabaa"

Output: 0

Assumptions:

N is an integer within the range [0, ..200,000];

String S consists of only characters a and b.