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

bccdb
 z
 dfdeed
 aab
 y
 abac

s1 = [ch for ch in input()]
s2 = [ch for ch in input()]

s1.sort()
s2.sort()

n = len(s1)

i1 = 0
i2 = n - 1

j1 = 0
j2 = n - 1

ans = ['?'] * n
for i in range(n):
    if (i % 2 == 0):
        if (s2[i2] < s1[i1]):
            ans[j2] = s1[i1]
            j2 -= 1
        else:
            ans[j1] = s1[i1]
            j1 += 1
        i1 += 1
    else:
        if (s1[i1] > s2[i2]):
            ans[j1] = s2[i2]
            j1 += 1
        else:
            ans[j2] = s2[i2]
            j2 -= 1
        i2 -= 1

print(''.join(ans))