Maija drives freight trains between the big cities of Europe. On her next trip, she is going to tow n cars numbered 1,2,\dots,n. The ID of the i-th car is a_i, which is a string consisting of at most 10 lowercase Latin letters. The cars should be ordered by their IDs. As no further standards restrict the IDs, sorting the cars by their IDs becomes confusing. Therefore, it has been decided that the cars should be sorted so that the concatenation of IDs is lexicographically minimal. Help Maija sort the cars.

Input

The first line contains a single integer n.

Each of the next n lines contains a single string a_i.

Output

Print the lexicographically minimal concatenation of the strings.

Constraints

• 1 \leq n \leq 10^5
• 1 \leq |a_i| \leq 10
• a_i \neq a_j if i \neq j

Example 2

Input:

3
ca
cab
de

Output:

cabcade

Example 1

Input:

10
acg
bcggd
dcg
dede
e
f
fc
fdbb
g
gabb

Output:

acgbcggddcgdedeefcfdbbfgabbg