Interesting Correspondence

Limits: 2 sec., 256 MiB

Marichka is going to take part in “Miss High School” contest and Zenyk is helping her to prepare. Since they want to keep all things secret they decided to encrypt e-mails related to the contest.

The guys are using the following cipher: if Zenyk has a message of length \(\mathbf{N} = K \cdot K\), for example ‘123456789’, he writes it down into a K by K square in a diagonal order starting from the top left corner

    124
    357
    689

Finally he concatenates the rows of the square and sends the message ‘124357689’ to Marichka.

Your task is to help Marichka to decode the given message.

Input

The first line contains integer N — the length of the message. The following line contains the message S Marichka has received.

Output

The original message.

Constraints

S contains only lowercase (’a’-’z’), uppercase (’A’-’Z’) English letters and digits (’0’-’9’),

\(|\mathbf{S}| = \mathbf{N}\),

\(\mathbf{N} = K^2\),

\(1 \le K \le 10\).

Samples