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C. The Smallest String Concatenation

time limit per test

3 secondsmemory limit per test

256 megabytesinput

standard inputoutput

standard outputYou'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

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