Study the following code. It *should* meet the following
specification, but it does not. Your task is to rewrite the code so
that it is correct.

The function `is_prime`

determines whether its input is a prime
number. Recall that a prime number is defined as those integers
(greater than 1) that are divisible by only themselves and 1 (of
course 1 divides every integer). So 7 is prime because the only
numbers that divide 7 are 7 itself and 1. But 9 is not prime because 9
is divisible by 3.

Here is a program that has the `is_prime`

function and a `main`

function. There are several errors in both functions. Rewrite the code
so it is correct.