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

bccdb
 z
 dfdeed
 aab
 y
 abac

import math
def get_res(s, t):
    N = len(s)
    reslist = ['']*N
    slist = sorted(s)
    tlist = sorted(t, reverse=True)
    sk = 0
    tk = 0
    flag = 0
    cnt = 0
    first = 0
    last = N-1
    while cnt < N:
        #print "N, cnt, sk, tk: ", N, cnt, sk, tk
        if flag == 0:
            if slist[sk] < tlist[tk]:
                reslist[first] = slist[sk]
                first += 1
            else:
                reslist[last] = slist[sk]
                last -= 1
            sk += 1
            flag = 1
        else:
            if tlist[tk] > slist[sk]:
                reslist[first] = tlist[tk]
                first += 1
            else:
                reslist[last] = tlist[tk]
                last -= 1
            tk += 1
            flag = 0
        cnt += 1

    return ''.join(reslist)

#N = int(raw_input())  

s = raw_input().split(" ")[0]
t = raw_input().split(" ")[0]
result = get_res(s, t)
print "{}".format(result)
