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

bccdb
 z
 dfdeed
 aab
 y
 abac

import sys

# oleg = min
# igor = max

def solve(oleg, igor):
    n = len(oleg)
    oleg = sorted(oleg)[:n/2 + 1 if n % 2 == 1 else n/2]
    igor = sorted(igor, reverse=True)[:n/2]
    arr = [""] * n
    fwd_ptr = 0
    rev_ptr = len(arr)-1

    f_oleg = 0
    r_oleg = len(oleg)-1

    f_igor = 0
    r_igor = len(igor)-1

    for char in range(n):
        if char == n-1:
            if n % 2 == 0:
                arr[fwd_ptr] = igor[f_igor]
            else:
                arr[fwd_ptr] = oleg[f_oleg]
        else:
            # oleg's turn
            if char % 2 == 0:
                if oleg[f_oleg] < igor[f_igor]:
                    arr[fwd_ptr] = oleg[f_oleg]
                    fwd_ptr += 1
                    f_oleg += 1
                else:
                    arr[rev_ptr] = oleg[r_oleg]
                    rev_ptr -= 1
                    r_oleg -= 1
            # igor's turn
            else:
                if oleg[f_oleg] >= igor[f_igor]:
                    arr[rev_ptr] = igor[r_igor]
                    rev_ptr -= 1
                    r_igor -= 1
                else:
                    arr[fwd_ptr] = igor[f_igor]
                    fwd_ptr += 1
                    f_igor += 1
    return "".join(arr)


if __name__ == "__main__":
    oleg = list(sys.stdin.readline().strip())
    igor = list(sys.stdin.readline().strip())
    print solve(oleg, igor)
