s1 = list(raw_input())
s2 = list(raw_input())
ans = []
while len(s1) != 0 and len(s2) != 0:
    if s1[0] == s2[0]:
        del s1[0]
        del s2[0]
    else:
        if s1[0].isalpha():
            if s1[0].upper() not in ans: 
                ans.append(s1[0].upper())
        else:
            if s1[0] not in ans:
                ans.append(s1[0])
        del s1[0]
while len(s1):
    if s1[0].isalpha():
            if s1[0].upper() not in ans: 
                ans.append(s1[0].upper())
    else:
        if s1[0] not in ans:
            ans.append(s1[0])
    del s1[0]
print ''.join(ans)