FOPviva

write a method encrypt(String word) that encrypts a word by doing the following algorithm:

    - remove the middle letter of the input word and append it to the encrypted word.
    - if the length of the input word is even, then take the letter on the left of the two median values.
    - repeat until there are no letters left in `word`.


example:

hello    ->    lelho
world    ->    rolwd
FOP      ->    OFP

explaination:

normal      "hello"     "helo"      "hlo"       "ho"        "o"         ""
encrypted   ""          "l"         "le"        "lel"       "lelh"      "lelho"


def encrypt(w):
    s = ''
    while w:
        l = (len(w) - 1) // 2
        s += w[l]
        w = w[:l] + w[l + 1:]
    return s

def decrypt(w):
    s = [w[-1]]
    w = w[:-1]
    while w:
        l = (len(s)) // 2
        s.insert(l, w[-1])
        w = w[:-1]
    return ''.join(s)