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

bccdb
 z
 dfdeed
 aab
 y
 abac

s1=input()
s2=input()
n=len(s1)
ss1=[]
ss2=[]
for i in range(n):
    ss1+=[s1[i]]
    ss2+=[s2[i]]
ss1.sort()
ss2.sort()
j=0
k=n-1
i=0
s=""
while i<n :
    if i%2==0:
        s+=ss1[j]
        j+=1
    else:
        s+=ss2[k]
        k-=1
    i+=1
print(s)