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Beautiful Binary
String
Alice has a binary string,
the substring

, of length

. She thinks a binary string is beautiful if and only if it doesn't contain

.

In one step, Alice can change a to a (or vice-versa). Count and print the minimum number of steps
needed to make Alice see the string as beautiful.
Input Format
The first line contains an integer, (the length of binary string
The second line contains a single binary string, , of length .

).

Constraints

Each character in

.

Output Format
Print the minimum number of steps needed to make the string beautiful.
Sample Input 0
7
0101010

Sample Output 0
2

Sample Input 1
5
01100

Sample Output 1
0

Sample Input 2
10
0100101010

Sample Output 2
3

Explanation

Sample Case 0:
In this sample,
The figure below shows a way to get rid of each instance of

Because we were able to make the string beautiful by changing

:

characters (

and

), we print .

Sample Case 1:
In this sample
The substring

does not occur in

, so the string is already beautiful and we print .



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Producer                        : Qt 4.8.4 (C) 2011 Nokia Corporation and/or its subsidiary(-ies)
Create Date                     : 2016:09:01 21:55:42Z
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