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

bccdb
 z
 dfdeed
 aab
 y
 abac

first = raw_input()
second = raw_input()

first = sorted([i for i in first])
second = sorted([i for i in second],reverse = True)

n = len(first)

ans = ['']*n
l = 0
r = n-1

f = first[:n/2]
s = second[:n/2]

if n % 2 != 0:
    f += first[n/2]


fl = 0
fr = len(f)-1

sl = 0
sr = len(s)-1

index = 0

while True:
    if index % 2 == 0: # First player

        if index == n-1:
            ans[l] = f[fl]
            break
    
        if f[fl] >= s[sl]:
            ans[r] = f[fr]
            r -= 1
            fr -= 1
        else:
            ans[l] = f[fl]
            l += 1
            fl += 1
        


    else: # second
        if index == n-1:
            ans[l] = s[sl]
            break
        
        if s[sl] <= f[fl]:
            ans[r] = s[sr]
            
            r -= 1
            sr -= 1
        else:
            ans[l] = s[sl]

            l += 1
            sl += 1

        
    index += 1

    
print ''.join(ans)


