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

bccdb
 z
 dfdeed
 aab
 y
 abac

from operator import lt, gt
s = [sorted(input()), sorted(input(), reverse=True)]
n = len(s[0])
idx = [[0, (n >> 1) + (n & 1) - 1], [0, (n >> 1) - 1]]
op = [lt, gt]
l, r = 0, n-1
ans = ['*'] * n

for i in range(n):
    p = i & 1
    if op[p](s[p][idx[p][0]], s[p ^ 1][idx[p ^ 1][0]]):
        ans[l] = s[p][idx[p][0]]
        l += 1
        idx[p][0] += 1
    else:
        ans[r] = s[p][idx[p][1]]
        r -= 1
        idx[p][1] -= 1

print(*ans, sep='')
