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

bccdb
 z
 dfdeed
 aab
 y
 abac

first = ''.join(sorted(raw_input()))
second = ''.join(sorted(raw_input()))[::-1]
ans=''
j = 0
k = 0
for i in range(len(first)) :
      if i%2==0 :
            ans += first[j]
            j += 1
      else :
            ans += second[k]
            k += 1
print ans            