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

bccdb
 z
 dfdeed
 aab
 y
 abac

mi=sorted([ord(x) for x in list(input())])
ma=sorted([ord(x) for x in list(input())],reverse=True)
c1=c2=0
for x in range(len(mi)):
	if x % 2 == 0:
		print(chr(mi[c1]),end='')
		c1+=1
	else:
		print(chr(ma[c2]),end='')
		c2+=1