c$++3\mathrm{.}24$ LAB: Interstate highway numbers

Primary U$.$S$.$ interstate highways are numbered $1-99.$ Odd numbers $($like the $5$ or $95)$ go north$/$south$,$ and evens $($like the $10$ or $90)$ go east$/$west$.$ Auxiliary highways are numbered $100-999,$ and service the primary highway indicated by the rightmost two digits. Thus, I$-405$ services I$-5,$ and I$-290$ services I$-90.$ Note: $200$ is not a valid auxiliary highway because $00$ is not a valid primary highway number.