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

bccdb
 z
 dfdeed
 aab
 y
 abac

import sys

def solve():
    s = input()
    t = input()

    n = len(s)
    s = sorted(s)[:(n + 1) // 2]
    t = sorted(t, reverse=True)[:n // 2]

    ans = [''] * n
    ansl = 0
    ansr = n - 1

    olgl = 0
    olgr = len(s) - 1
    igol = 0
    igor = len(t) - 1

    for i in range(n):
        if i % 2 == 0:
            if igol > igor or s[olgl] < t[igol]:
                ans[ansl] = s[olgl]
                ansl += 1
                olgl += 1
            else:
                ans[ansr] = s[olgr]
                ansr -= 1
                olgr -= 1
        else:
            if olgl > olgr or t[igol] > s[olgl]:
                ans[ansl] = t[igol]
                ansl += 1
                igol += 1
            else:
                ans[ansr] = t[igor]
                ansr -= 1
                igor -= 1

    print(''.join(ans))

if __name__ == '__main__':
    solve()