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 + 1) // 2]
t = t[:(n + 1) // 2]
#
ans = []
#
if s >= t:
    its = len(s) - 1
    itt = len(t) - 1
    for i in range(n):
        if i % 2 == 0:
            ans.append(s[its])
            its -= 1
        else:
            ans.append(t[itt])
            itt -= 1
    print(''.join(ans[::-1]))
else:
    its = 0
    itt = 0
    for i in range(n):
        if i % 2 == 0:
            ans.append(s[its])
            its += 1
        else:
            ans.append(t[itt])
            itt += 1
    print(''.join(ans))