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

bccdb
 z
 dfdeed
 aab
 y
 abac

s1 = str(raw_input())
s2 = str(raw_input())
a = []
b = []
for i in range(len(s1)):
	a.append(s1[i])
	b.append(s2[i])
a.sort()
b.sort()
b = b[::-1]
result = ""
for i in range(len(s1)):
	if i%2 == 0:
		result += a[0]
		a = a[1:]
	else:
		result += b[0]
		b = b[1:]
print result
