题解 | #找出字符串中第一个只出现一次的字符#

while True:
    try:
        #获取输入字符串
        x1 = input()
        #定义标签
        flag = 0
        
        d = {}
        for word in x1:
            if word not in d:
                d[word] = 1
            else:
                d[word] += 1
        list1 = list(d.values())
        if 1 not in list1:
            flag = 1
        if flag == 1:
            print(-1)
            break
        
        for k,v in enumerate(x1):
            if v not in x1[0:k] and v not in x1[k+1:]:
                print(v)
                break
    except:
        break