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

bccdb
 z
 dfdeed
 aab
 y
 abac

str1 = raw_input()
str2 = raw_input()
l1 =[]
l2=[]
for i in range(len(str1)):
	l1.append(str1[i])
	l2.append(str2[i])

l1 = sorted(l1)
l2 = sorted(l2,reverse=True)

final_ans=""

for i in range(len(l1)):
	if i%2==0:
		final_ans+=l1[0]
		del l1[0]
	else:
		final_ans+=l2[0]
		del l2[0]

print final_ans