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()
n = len(a)
u = v = ''
i, j = 0, -1
x, y = n - 1 >> 1, n - 2 >> 1
while x != -1:
    if a[i] < b[j]:
        u += a[i]
        i += 1
    else: v += a[i + x]
    x -= 1
    if y == -1: break
    elif a[i] < b[j]:
        u += b[j]
        j -= 1
    else: v += b[j - y]
    y -= 1
print(u + v[::-1])