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

bccdb
 z
 dfdeed
 aab
 y
 abac

from sys import *
f = lambda: sorted(stdin.readline()[:-1])
a, b = f(), f()
t, k = '', len(a) + 1 >> 1
for i, j in zip(a[:k], b[k:][::-1] + ['']): t += min(i + j, j + i)
print(t)