Repeating Cipher

给一个字符串,有如下机密规则: 对于一个字符$s_i$,将它复制i遍,然后放到加密串的末尾. 现在给出加密串,要求还原原串.

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 $ .

6
baabbb

bab

10
ooopppssss

oops

1
z

z