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

bccdb
 z
 dfdeed
 aab
 y
 abac

s1 = raw_input()
s2 = raw_input()

n = len(s1)

s1 = list(s1)
s1.sort()

s2 = list(s2)
s2.sort()

s2 = s2[::-1]

cnt_1 = len(s1)/2 + len(s1)%2
cnt_2 = len(s2)/2

s1 = s1[:cnt_1]
s2 = s2[:cnt_2]

arr = [ 0 for i in range(n)]

start = 0
end = n - 1

c1 = 0
c2 = 0

for i in range(n):
    #print s1,s2
    a_move = -1
    b_move = 26
    if len(s1) > 0 and c1 < len(s1): a_move = ord(s1[c1])-ord('a')
    if len(s2) > 0 and c2 < len(s2): b_move = ord(s2[c2])-ord('a')
    if i%2 == 0:
        if a_move < b_move:
            arr[start] = a_move
            start+=1
            c1+=1
        else:
            arr[end] = ord(s1[len(s1)-1])-ord('a')
            s1.pop()
            end-=1

    else:
        if b_move > a_move:
            arr[start] = b_move
            start+=1
            c2+=1
        else:
            arr[end] = ord(s2[len(s2)-1])-ord('a')
            s2.pop()
            end-=1

s = ""
for i in range(len(arr)):
    c = chr(ord('a')+arr[i])
    s += c
print s