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

bccdb
 z
 dfdeed
 aab
 y
 abac

s=[i for i in raw_input()]
t=[i for i in raw_input()]
n=len(s)
oi=0
ii=n-1
s.sort()
t.sort()
ci=0
c=0
ans=['' for i in range(n)]
f=0
while ci<n:
    if c%2:
        ans[ci]=t[ii]
        if f==1:
            ci+=2
            f=0
        else:
            ci+=1
        ii-=1
    else:
        if s[oi]>t[ii] and ci!=n-1:
            ci+=1
            f=1
        ans[ci]=s[oi]
        if f==1:
            ci-=1
        else:
            ci+=1
        oi+=1
    c+=1
print ''.join(ans)
