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

bccdb
 z
 dfdeed
 aab
 y
 abac

a = list(raw_input())
n = len(a)
a.sort()
b = list(raw_input())
b.sort()
c = ""
tot = 0
for i in xrange(n + 1 >> 1):
    c1 = a[i]
    c2 = b[n - i - 1]
    c += min(c1, c2)
    tot += 1 
    if (tot < n) :
        c += max(c1, c2)
        tot += 1
print c