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

if (n == 1):
    ans = [s1[0]]
else:
    for t in range(n):
        if (t % 2 == 0):
            if ((j1 < n) and (s2[j1] < s1[i1])):
                ans[k2] = s1[i2]
                k2 -= 1
                i2 -= 1
            else:
                ans[k1] = s1[i1]
                k1 += 1
                i1 += 1
        else:
            if ((i1 < n) and (s1[i1] > s2[j1])):
                ans[k2] = s2[j1]
                k2 -= 1
                j1 += 1            
            else:
                ans[k1] = s2[j2]
                k1 += 1
                j2 -= 1

print(''.join(ans))