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

bccdb
 z
 dfdeed
 aab
 y
 abac

s=str(raw_input())
l=str(raw_input())
s=list(s)
l=list(l)
s.sort()
l.sort()
n=len(s)
ans=['' for i in range(n)]
p,q=0,n-1
r,ss=(n-1)/2,(n+1)/2
f,b=0,n-1
for i in range(n):
    #print s[p],l[q],p,q
    if i%2==0:
        if s[p]<l[q]:          
            ans[f]= s[p]
            p+=1
            f+=1
        else:
            ans[b]=s[r]
            r-=1
            b-=1
    else:
        if s[p]<l[q]:          
            ans[f]= l[q]
            q-=1
            f+=1
        else:
            ans[b]=l[ss]
            ss+=1
            b-=1
    #print ans
ans_str=''
for i in ans:
    ans_str+=i
print ans_str