Zero String

You are given a binary string $S$ of length $N$. You are allowed to perform the following types of operations on string $S$: - Delete any **one** character from $S$, and concatenate the remaining parts of the string. For example, if we delete the third character of $S = 1101$, it becomes $S = 111$. - Flip all the characters of $S$. For example, if we flip all character of $S = 1101$, it becomes $S