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

bccdb
 z
 dfdeed
 aab
 y
 abac

a = list(input())
b = list(input())
name = [None for _ in range(len(a))]

a.sort()
b.sort(reverse=True)


ai = 0
aj = (len(a)+1)//2 -1
bi = 0
bj = len(b)//2 -1
turn = 0   # 0 -> player A
ansi = 0
ansj = len(name)-1
#print(a, b, ai, aj, bi, bj)
for _ in range(len(name)):

    if not turn:

        if a[ai] < b[bj]:
            name[ansi] = a[ai]
            ai += 1
            ansi += 1

        else:
            name[ansj] = a[aj]
            aj -= 1
            ansj -= 1

    else:

        if b[bi] > a[ai]:
            name[ansi] = b[bi]
            bi += 1
            ansi += 1

        else:
            name[ansj] = b[bj]
            bj -= 1
            ansj -= 1

    turn ^= 1

print(''.join(name))
