import sys
# 正确读取:一行输入,按空格分割成两个字符串
s, t = sys.stdin.readline().strip().split()
u1 = [] # 题目奇数位(Python下标0、2、4...)
u2 = [] # 题目偶数位(Python下标1、3、5...)
u_trans = []
u_final = []
# 合并阶段
u = s + t
# 拆分奇偶位(题目序号从1开始)
for i in range(len(u)):
if i % 2 == 0:
u1.append(u[i])
else:
u2.append(u[i])
# 两组分别按ASCII从小到大排序
u1.sort()
u2.sort()
# 严格 奇→偶 交错拼回
max_len = max(len(u1), len(u2))
for i in range(max_len):
if i < len(u1):
u_trans.append(u1[i])
if i < len(u2):
u_trans.append(u2[i])
# 调整进制转换
for j in u_trans:
if j not in "0123456789abcdefABCDEF":
u_final.append(j)
else:
num10 = int(j, 16)
bin4 = format(num10, "04b")
bin_rev = bin4[::-1]
hex_res = hex(int(bin_rev, 2))[2:].upper()
u_final.append(hex_res)
print("".join(u_final))