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

bccdb
 z
 dfdeed
 aab
 y
 abac

#[int(k) for k in raw_input().split(" ")]
o=raw_input()
i=raw_input()
so=sorted(o)
si=sorted(i)
res=[None]*len(o)
k=0
n=len(o)
who=1
j=0
while j<n:
    res[j]=so[k] if who else si[n-1-k]
    who=1-who
    if who==1:
        k+=1
    j+=1

print "".join(res)