EntryTest4

my_list = []
#read input
my_input = input()
while(len(my_input) > 0):
    my_list.append(my_input)
    my_input = input()
#process the result
def cmp(s):
    return s
my_list = sorted(my_list, reverse = True)
#write the result
print("".join(my_list))