class TrieNode:
    def __init__(self):
        self.children = {}
        self.is_end_of_word = False

class Trie:
    def __init__(self):
        self.root = TrieNode()
    
    def insert(self, word):
        node = self.root
        for char in word:
            if char not in node.children:
                node.children[char] = TrieNode()
            node = node.children[char]
            # If we reach a node that is the end of another word, it's a BAD SET
            if node.is_end_of_word:
                return False
        # Mark the end of this word
        node.is_end_of_word = True
        # If this word is a prefix of any existing word, it's a BAD SET
        if node.children:
            return False
        return True

def noPrefix(words):
    trie = Trie()
    for word in words:
        if not trie.insert(word):
            print("BAD SET")
            print(word)
            return
    print("GOOD SET")