It is Raful's birthday, and his friends gave him $$N$$ strings of length $$M$$. But he is not happy, because he wants only one beautiful string $$S$$.
His friends are upset now. You, as the best programmer in Lalalandia, decided to help them.
The string $$S$$ is considered beautiful only when the sum of the Hamming distances between it and each of the $$N$$ strings is minimal. If there exist several such strings, print out the lexicographically smallest one.
The first line of the input contains two integers $$N$$, $$M$$ - number of strings and their lengths respectively.
Then $$N$$ lines follow, each containing a string $$s_i$$ ($$1 \le i \le N$$), each consists of lowercase English letters.
The only line of the output should contain the string $$S$$.
$$1 \le N * M \le 100000$$
You can learn more about Hamming distance here:
In this sample, "a" is lexicographically minimal string among all valid answers.