Jumping Robot

A city has $N$ streets numbered from $0$ to $N-1$. The organization of the city is given to us as a string $S$ of length $N$ (with only lowercase letters) where the ith position represents the ith street (i starts from $0$). In each street, there are only *S[i]*th types of houses. A newspaper agency has to deliver their newspapers to each house of all the streets. The agency decides to provide $