I found an interesting problem on https://www.codewars.com/kata/580a0347430590220e000091:
Find the area of a rectangle when provided with one diagonal and one side of the rectangle. If the input diagonal is less than or equal to the length of the side, return "Not a rectangle". If the resultant area has decimals round it to two places.

`This kata is meant for beginners. Rank and upvote to bring it out of beta!`

I tried it in Python, but could not do it. Can you solve it?
def area(d, l):
    if d <= l: return 'Not a rectangle'
    a = l * (d ** 2 - l ** 2) ** 0.5
    return round(a, 2) if a % 1 else int(a)