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

bccdb
 z
 dfdeed
 aab
 y
 abac

s = list(input())
t = list(input())

s = sorted(s, reverse=True)
t = sorted(t)

ans = ""
for i in range(len(s)):
    ans += s.pop() if i & 1 == 0 else t.pop()

print(ans)
