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

bccdb
 z
 dfdeed
 aab
 y
 abac

def main():
    from collections import deque
    import sys
    input = sys.stdin.readline
    
    s = list(input())[:-1]
    t = list(input())[:-1]
    n = len(s)
    s.sort()
    t.sort(reverse=True)
    s = deque(s[:(n + 1) // 2])
    t = deque(t[:n // 2])
    f = 0
    al, ar = "", ""
    for i in range(n):
        if i % 2:
            if s and s[0] >= t[0]: f = 1
            if f: ar += t.pop()
            else: al += t.popleft()
        else:
            if t and s[0] >= t[0]: f = 1
            if f: ar += s.pop()
            else: al += s.popleft()
    print(al + ar[::-1])
if __name__ == '__main__':
    main()
    