# https://open.kattis.com/problems/classfieldtrip
# 1s
# 1.4 Easy

# The shortest Python3 program are 38 chars

print("".join(sorted(input()+input())))


# 39 chars 
# print("".join(sorted(input()+input())))

# 43 chars
# print(sorted((input()+input()).split())[0])