d = dict()
dict1 = dict()
dict2 = dict()
for i in range(26):
    d[chr(97 + i)] = i
    dict1[chr(97 + i)] = 0
    dict2[chr(97 + i)] = 0
name1 = list(input())
name2 = list(input())
for i in name1:
    dict1[i] += 1
for i in name2:
    dict2[i] += 1
i1 = 0
i2 = 0
a = []
while i1 < len(name1) and i2 < len(name2):
    if dict2[name1[i1]] == 0:
        i1 += 1
        continue
    if dict1[name2[i2]] == 0:
        i2 += 1
        continue
    if name1[i1] == name2[i2]:
        while len(a) != 0 and d[name1[i1]] > d[a[-1]]:
            a.pop()
        a.append(name1[i1])
        dict1[name1[i1]], dict2[name2[i2]] = dict1[name1[i1]] - 1, dict2[name2[i2]] - 1
        i1, i2 = i1 + 1, i2 + 1
    elif d[name1[i1]] > d[name2[i2]]:
        dict2[name2[i2]] -= 1
        i2 += 1
    else:
        dict1[name1[i1]] -= 1
        i1 += 1

while i2 >= len(name2) and name2[i2-1] != name1[i1-1] and i1 < len(name1):
    i1 += 1
    if name2[i2-1] == name1[i1-1]:
        while len(a) != 0 and d[name1[i1]] > d[a[-1]]:
            a.pop()
        a.append(name1[i1])
while i1 >= len(name1) and name2[i2-1] != name1[i1-1] and i2 < len(name2):
    i2 += 1
    if name2[i2-1] == name1[i1-1]:
        while len(a) != 0 and d[name2[i2]] > d[a[-1]]:
            a.pop()
        a.append(name1[i2])

print(''.join(a))