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

bccdb
 z
 dfdeed
 aab
 y
 abac

import sys
import heapq
import math

a = []
b = []


def read_line(arr):
    while True:
        c = sys.stdin.read(1)
        if c == '\n' or c == '':
            break
        heapq.heappush(arr, c)


s = []
r = []
read_line(a)
read_line(b)
n = len(a)

a = heapq.nsmallest(math.ceil(n / 2), a)
b = heapq.nlargest(math.floor(n / 2), b)
left = [0, 0]
right = [-1, -1]
for i in range(n):
    turn = i % 2
    arr = a if turn == 0 else b
    if i == n - 1 or a[left[0]] < b[left[1]]:
        s.append(arr[left[turn]])
        left[turn] += 1

    else:
        r.append(arr[right[turn]])
        right[turn] -= 1
for i in s:
    print(i, end='')
for i in range(len(r)):
    print(r[~i], end='')
