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]

# print('A', A)
# print('B', B)

ans = [None] * n
front_i = 0
back_i = n - 1
for i in range(n):
    if i % 2 == 0:
        if B:
            if A[-1] > B[0]:
                ans[back_i] = A.pop(-1)
                back_i -= 1
            else:
                ans[front_i] = A.pop(0)
                front_i += 1
        else:
            ans[front_i] = A.pop(0)
            front_i += 1

    else:
        if A:
            if A[-1] > B[0]:
                ans[back_i] = B.pop(-1)
                back_i -= 1
            else:
                ans[front_i] = B.pop(0)
                front_i += 1
        else:
            ans[front_i] = B.pop(0)
            front_i += 1

print(''.join(ans))