Tracy has a string of lowercase alphabetical characters. She would like to choose a point on her string between two characters to be the center of a special palindrome. She can remove characters from the beginning or end of the string to make her special palindrome.

A palindrome is defined as special if it has of the same letter in the center, and each letter from the center is repeated times, where is the distance from the center. That is, the center of the palindrome should have of the same letter, then , then , and so on. In addition, each repeated section of the same letter should be of a different letter than those adjacent to it.

Can you output the length of the longest special palindrome Tracy can make?

#### Input Specification

The first line will contain one integer , the length of Tracy's string.

The next line will contain lowercase alphabetical characters, Tracy's string.

#### Output Specification

Output a single integer, the length of the longest special palindrome Tracy can make. If Tracy cannot make a special palindrome, output `-1`

.

#### Sample Input 1

```
36
aloifinoddddbbbzzbbbddddllakwifoidgl
```

#### Sample Output 1

`16`

#### Explanation for Sample 1

The longest special palindrome Tracy can make is `ddddbbbzzbbbdddd`

.

#### Sample Input 2

```
30
slkdgjsngasdioawiawjklgawleawf
```

#### Sample Output 2

`-1`

## Comments