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

bccdb
 z
 dfdeed
 aab
 y
 abac

s = list(input())
t = list(input())
n = len(s)

ss = list(sorted([c for c in s]))[:(n + 1) // 2]
st = list(reversed(sorted([c for c in t])))[:n // 2]

ans = ""
r = 1 if (n % 2 == 0 and st[-1] < ss[0]) else 0
for i in range(n):
    if i % 2 == r:
        ans += ss[i // 2]
    else:
        ans += st[i // 2]

print(''.join(ans))
