CF1095A.Repeating Cipher

Polycarp loves ciphers. He has invented his own cipher called repeating.

Repeating cipher is used for strings. To encrypt the string $s=s_{1}s_{2} \dots s_{m}$ ( $1 \le m \le 10$ ), Polycarp uses the following algorithm:

• he writes down $s_1$ ones,
• he writes down $s_2$ twice,
• he writes down $s_3$ three times,
• ...
• he writes down $s_m$ $m$ times.

For example, if $s$ ="bab" the process is: "b" $\to$ "baa" $\to$ "baabbb". So the encrypted $s$ ="bab" is "baabbb".

Given string $t$ — the result of encryption of some string $s$ . Your task is to decrypt it, i. e. find the string $s$ .

The first line contains integer $n$ ( $1 \le n \le 55$ ) — the length of the encrypted string. The second line of the input contains $t$ — the result of encryption of some string $s$ . It contains only lowercase Latin letters. The length of $t$ is exactly $n$ .

It is guaranteed that the answer to the test exists.

Print such string $s$ that after encryption it equals $t$ .