Write a rotate$()$ function that takes two parameters, a string intended to be one upper$-$case A$-$Z letter and an integer, and returns a string. The returned string should be the $*$input letter rotated by the number of positions specified by the integer argument. $($The Romans of Caesar's time only used what today we call upper$-$case letters.$)$

So a call to rotate$(\text{'}$C$\text{'},1)$ should return $($return not print$)$ the string $\text{'}$D$\text{'}$ and a call to rotate$(\text{'}$D$\text{'},-1)$ should return the string $\text{'}$C$\text{'}.$ Rotation should "wrap around" the end of the alphabet, so rotate$(\text{'}$Z$\text{'},3)$ should return $\text{'}$C$\text{'}.$