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

bccdb
 z
 dfdeed
 aab
 y
 abac

a=sorted(list(raw_input()))
b=sorted(list(raw_input()))
s=[None]*len(a)
c=0
d=0
for i in range(len(a)):
    if i%2==0:
        if a[0]<b[-1]:
            s[d]=a[0]
            d+=1
            a.pop(0)
        else:
            s[-1-c]=a[-1]
            c+=1
            a.pop(-1)
    else:
        if b[-1]>a[0]:
            s[d]=b[-1]
            d+=1
            b.pop(-1)
        else:
            s[-1-c]=b[0]
            c+=1
            b.pop(0)
k=''
for i in s:k+=i
print k