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

bccdb
 z
 dfdeed
 aab
 y
 abac

from __future__ import division
from sys import stdin
from math import ceil
from collections import *

rstr = lambda: stdin.readline().strip()
s, t = sorted(rstr()), sorted(rstr(), reverse=True)
le = len(s)
s, t = deque(s[:int(ceil(le / 2))]), deque(t[:le >> 1])
be, en = [], []

for i in range(le):
    if i & 1:
        if not s or t[0] > s[0]:
            be.append(t.popleft())
        else:
            en.append(t.pop())
    else:
        if not t or s[0] < t[0]:
            be.append(s.popleft())
        else:
            en.append(s.pop())

print(''.join(be + en[::-1]))
