You are given a binary string s of length n. Each character '1' in s represents an active section.

You are allowed to perform at most one trade operation:

• Select a contiguous substring of '1's that is immediately flanked by '0's on both its left and right sides.

• Let $A$ be the maximal contiguous block of '0's immediately to the left of the selected substring, and let $B$ be the maximal contiguous block of '0's immediately to its right.

• The trade operation converts all characters in both $A$ and $B$ into '1's.

Return the maximum number of active sections in s after performing at most one trade operation.

Constraints:

• $1 \leq n ==$ s.length $\leq 10^5$

• s[i] is either '0' or '1'

Now, let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Implement your solution in the following coding playground.