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

bccdb
 z
 dfdeed
 aab
 y
 abac


a=raw_input()
b=raw_input()

a=sorted(a)
b=sorted(b,reverse=True)

ans=""

x=0
y=0
for i in range(len(a)):
    if i%2==0:
        ans+=a[x]
        x=x+1
    else:
        ans+=b[y]
        y=y+1
         
print ans