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

bccdb
 z
 dfdeed
 aab
 y
 abac

s = list(input())
t = list(input())
n = len(s)
ans = [0]*n
i = 0
j = 0
k = n-1
s.sort()
t.sort()
while (i<n and s[j]<=t[n-j-1]):
    ans[i] = s[j]
    if (i+1<n):
        ans[i+1] = t[n-j-1]
    i += 2
    j += 1
while (k>=i):
    ans[k] = s[j]
    if (k>=i):
        ans[k-1] = t[n-j-1]
    k -= 2
    j += 1
answer = ""
for m in ans:
    answer += m
print(answer)
