Description

Original source: HNOI 2006

Given $n$ strings $S_1,S_2,\cdots ,S_n$, find the shortest string $T$ such that all $n$ strings are substrings of $T$.

Input Format

The first line contains a positive integer $n$, indicating the number of given strings;

The following $n$ lines each contain a string composed entirely of uppercase letters.

Output Format

Output only one line, the shortest string $T$ found.

If there are multiple strings that satisfy the requirement while being the shortest, the one that comes first in lexicographical order must be output.

Sample 1

2
ABCD
BCDABC

ABCDABC

Data Range and Hint

For all data, $1\le n\le 12,1\le |S_i|\le 50$.