String Decoration

Time limit

Memory limit

128 MB

Problem

Minsik wants to make one string W from N given words.

He may first split each word into any number of pieces. Then he concatenates all pieces to make W. The pieces that came from the same word must keep their original order in that word.

For instance, suppose he has the three words {YOUNGSIK, DONGHO, ALGORITHM}. He could split them into pieces such as {YOUNG, SIK, DO, NG, HO, AL, GO, RITHM}, then concatenate the pieces as shown below.

YOUNG     SIK     DO      NG    HO       AL      GO    RITHM--------------------------YOUNGDOALSIKNGGOHORITHM

YOUNG     SIK     DO      NG    HO       AL      GO    RITHM--------------------------YOUNGDOALSIKNGGOHORITHM

Print the lexicographically smallest string that Minsik can make.

Input

The first line contains the number of words N. N is at most 20.

Each of the next N lines contains one word. Each word has length at most 1,000 and consists only of uppercase English letters, with no spaces.

Output

Print the lexicographically smallest string that can be made.