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

bccdb
 z
 dfdeed
 aab
 y
 abac

s, t = raw_input(), raw_input()

s, t = list(s), list(t)

s.sort(cmp=lambda x, y: cmp(x, y))
t.sort(cmp=lambda x, y: -cmp(x, y))

l = len(s)
t = t[:l/2]
if l % 2 == 0:
    s = s[:l/2]
else:
    s = s[:l/2+1]
res = ['' for i in xrange(l)]
a, b = 0, l-1
x1, x2 = 0, 0
y1, y2 = len(s)-1, len(t)-1
for i in xrange(l):
    if i%2 == 0:
        if x2 > y2:
            res[a] = s[x1]
            a += 1
            x1 += 1
        elif s[x1] >= t[x2]:
            res[b] = s[y1]
            y1 -= 1
            b -= 1
        else:
            res[a] = s[x1]
            a, x1 = a+1, x1+1
    else:
        if x1 > y1:
            res[a] = t[x2]
            a += 1
            x2 += 1
        elif s[x1] >= t[x2]:
            res[b] = t[y2]
            y2 -= 1
            b -= 1
        else:
            res[a] = t[x2]
            a, x2 = a+1, x2+1
if a<b:
    while True:
        pass
print ''.join(res)
