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

bccdb
 z
 dfdeed
 aab
 y
 abac

# -*- coding: utf-8 -*-

import sys
import os
import math

# input_text_path = __file__.replace('.py', '.txt')
# fd = os.open(input_text_path, os.O_RDONLY)
# os.dup2(fd, sys.stdin.fileno())

A = sorted(list(input()))
B = sorted(list(input()))
A.sort()
B.sort(reverse=True)
n = len(A)

if n % 2 == 0:
    A = A[:n//2]
    B = B[:n//2]
else:
    A = A[:n // 2 + 1]
    B = B[:n // 2]

ans = []
reverse_mode = False

for i in range(n):

    # 残りの箱が偶数
    if (n - len(ans)) % 2 == 0 and B[-1] < A[0]:
        #print('reverse', A, B)
        reverse_mode = True

    if reverse_mode:
        if i % 2 == 0:
            ans.append(B.pop(0))
        else:
            ans.append(A.pop(0))
    else:
        if i % 2 == 0:
            ans.append(A.pop(0))
        else:
            ans.append(B.pop(0))
print(''.join(ans))