fbkihomeworks/13.10.2026/var4/problem2.py

def is_rune_word(word):
    if not word[0].isupper():
        return False
    length = 0
    for letter in word:
        if letter.isupper():
            if length != 0 and (length < 2 or length > 4):
                return False
            length = 1
        else:
            length += 1
    return 2 <= length <= 4


word = input()
if is_rune_word(word):
    print("Yes")
else:
    print("No")