백준 3244 두 부분 문자열 2(실패)

https://www.acmicpc.net/problem/3244

3244번: 두 부분 문자열 2

A=input()
B=input()
if len(A)>=len(B):
    result=A
else:
    result=B
for i in range(len(A)):
    for j in range(i+1,len(A)):
        if A[i:j] not in B:
            if len(A[i:j])<len(result):
                result=A[i:j]
print(result)

import itertools
A=input()
B=input()
L=[]
cnt=0
for i in range(len(A)):
    if cnt ==1:
        break
    L.append(list(map(''.join, itertools.combinations(A,i+1))))
    L[i]=list(set(L[i]))
    for j in range(len(L[i])):
        if L[i][j] not in B:
            print(L[i][j])
            cnt+=1
            break