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

bccdb
 z
 dfdeed
 aab
 y
 abac

s = list(raw_input())
t = list(raw_input())
s.sort()
t.sort()
n = len(s)
i = 0
j = n-1
k = 0
ans = [None]*n
while k < n and s[i] <= t[j]:
    if k % 2 == 0:
        ans[k] = s[i]
        i += 1
    else:
        ans[k] = t[j]
        j -= 1
    k += 1
rev = n-1
i = (n+1)/2-1
j = n-n/2
while k < n:
    if k % 2 == 0:
        ans[rev] = s[i]
        i -= 1;
    else:
        ans[rev] = t[j]
        j += 1
    k += 1; rev -= 1
print "".join(map(str, ans))
