while True: try: s = input() dic = {} #字典 for i in s: dic[i] = dic.get(i, 0)+1 #遍历更新值 if sum(dic.values())/len(dic) >= 2: #若无只出现一次的字符,打印-1 print(-1) else: for k in dic.keys(): if dic[k]==1: ...