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 // 2 - 1 + n % 2

j1 = n // 2 + n % 2
j2 = n - 1

k1 = 0
k2 = n - 1

#print(s1)
#print(s2)

ans = ['?'] * n
for t in range(n):
    if (t % 2 == 0):
        if (s2[i2] < s1[i1]):
            ans[k2] = s1[i2]
            k2 -= 1
            i2 -= 1
        else:
            ans[k1] = s1[i1]
            k1 += 1
            i1 += 1
    else:
        if (s1[i1] > s2[i2]):
            ans[k2] = s2[j1]
            k2 -= 1
            j1 += 1            
        else:
            ans[k1] = s2[j2]
            k1 += 1
            j2 -= 1

print(''.join(ans))