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()))[::-1]
s=''
for i in range(len(a)):
    if i%2==0:s+=a[i/2]
    else:s+=b[i/2]
print s