Robots Again

You are given a string $s$ with length $N$ describing a row of cells numbered $1$ through $N$. Each character of this string is either a digit ('0' through '9', inclusive) or a dot ('.'). For each $i$ ($1 \le i \le N$), if the $i$-th character of $s$ is '.', the $i$-th cell is empty; if this character is the digit $d$, the $i$-th cell contains a robot that is able to move in a fixed range — betwee