class TriNode:
    def __init__(self):
        self.childs={}
        self.end_word=False

class Trie:
    def __init__(self):
        self.root = TriNode()
    def add(self, s):
        cur = self.root
        for ch in s:
            if ch in cur.childs:
                cur = cur.childs[ch]
                if cur.end_word:
                    return True #cases like ab, abc, when checks b in abc
            else:
                new_node = TriNode()
                cur.childs[ch] = new_node
                cur = new_node
        cur.end_word=True
        return cur.childs  #cases like abc, ab, when checking ab


def noPrefix(words):
    t = Trie()
    for w in words:
        p = t.add(w)
        if p:
            print(f"BAD SET\n{w}")
            return
    print("GOOD SET")