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