Use OCaml to write a program that returns one of four string values for each street

number:

$"$N$/$A$"$ when the street doesn't exist. We only consider $1$st

through $69$th Streets.

$"$N$"$ when the street goes north.

$"$S$"$ when the street goes south.

$"$NS$"$ when the street is two$-$way.

Hints:

You may find the infix 'mod' $($modulo$)$ function useful: for example,

$\text{'}x$ mod $2\text{'}$ evaluates to $0$ if $x$ is even and $1$ otherwise.

Sometimes there is no simple$/$clever way of writing down a

complex case analysis: you just have to write out all the cases.