题解 | #找出字符串中第一个只出现一次的字符#

import sys
def findonlyone(dic):
    for key, value in dic.items():
        if value == 1:
            return key
    return -1

dic = {}
for line in sys.stdin:
    a = line.strip()
    for i in a:
        dic[i] = dic.get(i, 0) + 1
sorted_dic = dict(sorted(dic.items(), key = lambda x: x[1]))
print(findonlyone(sorted_dic))