Access Control

Chef is a visitor in CodeChef's new office. All doors inside the office require a swipe of access card. The access card allows a fixed number of swipes and expires after that. You are given a **binary** string $S$ of length $N$ and an integer $X$. Let $S_i = 0$ denote the swipe of access card, thus reducing the remaining swipes by $1$; and $S_i = 1$ denote a renewal of access card which **set