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

bccdb
 z
 dfdeed
 aab
 y
 abac

O = []
I = []
s = input()
for i in s:
    O.append(i)
s = input()
for i in s:
    I.append(i)
O = sorted(O)
I = sorted(I)

ans = ''
n = len(O)
l = 0
r = n-1

for i in range(n):
    if i % 2 == 0:
        ans += O[l]
        l += 1
    else:
        ans += I[r]
        r -= 1

print(ans)