# Abgabe - Counting Duplicates Aufgabe von Codewars
# Link dazu: https://www.codewars.com/kata/54bf1c2cd5b56cc47f0007a1
# Leart Ramushi


def duplicate_count(text):
    lower_text = text.lower()
    letter_set = set()

    for i in range(len(lower_text)):
        if lower_text.count(lower_text[i]) > 1:
            letter_set.add(lower_text[i])

    return len(letter_set)