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

bccdb
 z
 dfdeed
 aab
 y
 abac

s1 = input().replace('', ' ')
t1 = input().replace('', ' ')
s = list(s1.split())
t = list(t1.split())
#
s.sort()
t.sort(reverse = True)
#
n = len(s)
s = s[:n // 2 + 1]
t = t[:n // 2 + 1]
#
front = []
back = []
zn = 0
#
scf = 0
#
tcf = 0
tcb = n // 2 - 1
#
while zn < n:
    if zn % 2 == 0 and s[scf] > t[tcf]:#O
        back.append(s[scf])
        scf += 1
    elif zn % 2 != 0 and s[scf] > t[tcf]:#I
        back.append(t[tcb])
        tcb -= 1
    elif zn % 2 == 0 and s[scf] <= t[tcf]:#O
        front.append(s[scf])
        scf += 1
    elif zn % 2 != 0 and s[scf] <= t[tcf]:#I
        front.append(t[tcf])
        tcf += 1
    zn += 1
print(''.join(front) + ''.join(back[::-1]))