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

bccdb
 z
 dfdeed
 aab
 y
 abac

s1=str(input())
s2=str(input())
n=len(s1)
list1=list(s1)
list1.sort()
list2=list(s2)
list2.sort()
list2.reverse()
#print(list1)
#print(list2)
list3=[]
for i in range(1,n+1):
    if i%2!=0:
        list3.append(list1[0])
        list1.remove(list1[0])
    else:
        list3.append(list2[0])
        list2.remove(list2[0])
print(''.join(list3))