You're given a list of n strings a_1, a_2, ..., a_{n}. You'd like to concatenate them together in some order such that the resulting string would be lexicographically smallest.

Given the list of strings, output the lexicographically smallest concatenation.


-----Input-----

The first line contains integer n — the number of strings (1 ≤ n ≤ 5·10^4).

Each of the next n lines contains one string a_{i} (1 ≤ |a_{i}| ≤ 50) consisting of only lowercase English letters. The sum of string lengths will not exceed 5·10^4.


-----Output-----

Print the only string a — the lexicographically smallest string concatenation.


-----Examples-----
Input
4
abba
abacaba
bcd
er

Output
abacabaabbabcder

Input
5
x
xx
xxa
xxaa
xxaaa

Output
xxaaaxxaaxxaxxx

Input
3
c
cb
cba

Output
cbacbc