Balanced Reversals

Chef is given a binary string $A$ of length $N$. He can perform the following operation on $A$ any number of times: - Choose $L$ and $R$ $(1 \leq L \leq R \leq N)$, such that, in the [substring](https://en.wikipedia.org/wiki/Substring) $A[L,R]$, the number of $1$s is **equal** to the number of $0$s and **reverse** the substring $A[L,R]$. Find the lexicographically **smallest** string that Chef ca