Short Message 2

The Space Research Center has identified $N$ planets, each with a name $S_i$ made up only of lowercase Latin letters. The researchers think that if some of these planets have intelligent life, they will reply to a message that contains the planet's name.

Sending cosmic messages is expensive, so we need a message that is as short as possible and contains all $N$ planet names as substrings.

Recall that a string $s$ is a substring of a string $t$ if $s$ can be obtained from $t$ by deleting some characters from the beginning and the end of $t$.

The first line of the input file contains the number of planets $N$. Each of the next $N$ lines contains one planet name $S_i$.

Print on the single line of the output file a message made of lowercase Latin letters that contains all $N$ planet names as substrings.