def shortest_completing_word(license_plate, words):
    normalized_license_plate = ''.join(char.lower() for char in license_plate if char.isalpha())

    shortest_word = None

    for word in words:
        # Check if current word contains all letters
        word_contains_all_letters = True
        for char in set(normalized_license_plate):
            if word.lower().count(char) < normalized_license_plate.lower().count(char):
                word_contains_all_letters = False
                break

        # Update shortest word if applicable
        if word_contains_all_letters:
            if shortest_word is None or len(word) < len(shortest_word):
                # Update shortest_word
                shortest_word = word

    return shortest_word

def shortestCompletingWord(license_plate, words):
    license_plate_letter_counts = {}
    for char in license_plate:
        if char.isalpha():
            lower_char = char.lower()
            license_plate_letter_counts[lower_char] = license_plate_letter_counts.get(lower_char, 0) + 1

    shortest_completing_word = None

    for word in words:
        word_letter_counts = {}
        for char in word:
            word_letter_counts[char] = word_letter_counts.get(char, 0) + 1

        completes = True
        # Ensure the word has all the letters from the license plate
        for letter, count in license_plate_letter_counts.items():
            if letter not in word_letter_counts or word_letter_counts[letter] < count:
                completes = False
                break

        if completes:
            # Update if current word is shorter
            if shortest_completing_word is None or len(word) < len(shortest_completing_word):
                shortest_completing_word = word

    return shortest_completing_word