class Solution:
def mostCommonWord(self, paragraph: str, banned: List[str]) -> str:
# Remove punctuation symbols
s = ''
for c in paragraph:
if c not in "!?',;.":
s += c
else:
s += ' '
paragraph = s.lower()
banned = set(banned + [''])
words = [w for w in paragraph.split(' ') if w not in banned]
return collections.Counter(words).most_common(1)[0][0]