Two-Tone Fence

Easy

A fence is made of boards, each painted white ('0') or black ('1'). The string fence lists the boards from left to right. The owner wants the colours to alternate, so that no two neighbouring boards share a colour. One action repaints a single board in the other colour. Return the minimum number of repaints.

Example 1

fence="00110" → 2

Repainting the second and the fourth boards gives "01010", which takes 2 repaints. Reaching "10101" would take 3.

Example 2

fence="1010" → 0

The colours already alternate, so nothing needs repainting.

Example 3

fence="000" → 1

Constraints

1 ≤ len(fence) ≤ 10⁴
fence contains only the characters '0' and '1'

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Input

fence="00110"

Expected

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