题解 | #找出字符串中第一个只出现一次的字符#

s = input() # asdfasdfoe
dic = {}
res = []
for i in s:
    if i not in dic:
        dic[i] = s.count(i)
        if dic[i] == 1:
            res.append(i)
#print(dic)
#print(res)     
if min(dic.values()) > 1:   
    print(-1)
else:       # 出现次数等于1
    print(res[0])