bcdef
abbbc
 z
y
 reddit
abcdef
 abc
aaa
 y
z
 cbxz
aaaa

bccdb
 z
 dfdeed
 aab
 y
 abac

s1 = input()
s2 = input()

s1 = sorted(s1)
s2 = sorted(s2)[::-1]

i = 0
j = 0

res = ""

for k in range(len(s1)):
    if i == j:
        res += s1[i]
        i += 1
    else:
        res += s2[j]
        j += 1
print(res)