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

bccdb
 z
 dfdeed
 aab
 y
 abac

s1=raw_input()
s2=raw_input()
a,b=[],[]
for i in range(len(s1)):
	a.append(s1[i])
	b.append(s2[i])
a=sorted(a)
b=sorted(b)
a1,b1,s,la,turn=0,len(b)-1,['-']*len(a),len(a)-1,0
if len(a) % 2 == 0:
	a11,b11=len(a)/2,len(a)/2
else:
	a11,b11=len(a)/2 + 1,len(a)/2
a11-=1
# b11-=1
fa=0
for i in range(len(a)):
	if turn == 0: 
		if a[a1] < b[b1]:
			# print 'If of 1'
			s[fa]=a[a1]
			fa+=1
			a1+=1
		else:
			# print 'Else of 1'
			s[la]=a[a11]
			a11-=1
			la-=1
	else: 
		if a[a1] < b[b1]:
			# print 'If of 2'
			s[fa]=b[b1]
			fa+=1
			b1-=1
		else:
			# print 'Else of 2'
			s[la]=b[b11]
			la-=1
			b11+=1
			# la-=1
	turn = (turn+1)%2
	# print s
s1=''
for i in s: s1+=i
print s1