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

bccdb
 z
 dfdeed
 aab
 y
 abac

first = (sorted(raw_input()))
second = (sorted(raw_input()))[::-1]
ans=[]
for i in range(len(first)) :
      if i%2==0 :
            if first[0] > second[0] :
                  break
            ans.append(first[0])
            del first[0]
      else :
            ans.append(second[0])
            del second[0]
if len(ans) < len(first) :
      for i in range(len(second)/2) :
            ans.append(second[i])
      for i in range(len(first)/2) :
            ans.append(first[i])
print ''.join(ans)    