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

bccdb
 z
 dfdeed
 aab
 y
 abac

s1 = list(raw_input())
s2 = list(raw_input())
n = len(s1)
s1.sort(); s2.sort()
i = 0; j = n-1


#i oleg
#j other.

s = ''

for k in range(n):
	if k%2 == 0:
		s = s+s1[i]
		i+=1
	else:
		s = s + s2[j]
		j -= 1

print s