import string

class Solution(object):
    def commonChars(self, A):
        """
        :type A: List[str]
        :rtype: List[str]
        """
        num_strings = len(A)
        letter_string_counts = {}
        common_letters = []

        for letter in string.ascii_lowercase:
            letter_string_counts[letter] = {}

            for idx, _ in enumerate(A):
                letter_string_counts[letter][idx] = 0

        for idx, _ in enumerate(A):
            for letter in A[idx]:
                letter_string_counts[letter][idx] += 1

        for letter in letter_string_counts:
            if len(letter_string_counts[letter]) == num_strings:
                min_occurence_amount = num_strings

                for idx in letter_string_counts[letter]:
                    min_occurence_amount = min(min_occurence_amount, letter_string_counts[letter][idx])

                common_letters += [letter] * min_occurence_amount

        return common_letters