### Problem Statement

For a positive integer $L$, a level-$L$ dango string is a string that satisfies the following conditions.

-   It is a string of length $L+1$ consisting of `o` and `-`.
-   Exactly one of the first character and the last character is `-`, and the other $L$ characters are `o`.

For instance, `ooo-` is a level-$3$ dango string, but none of `-ooo-`, `oo`, and `o-oo-` is a dango string (more precisely, none of them is a level-$L$ dango string for any positive integer $L$).

You are given a string $S$ of length $N$ consisting of the two characters `o` and `-`. Find the greatest positive integer $X$ that satisfies the following condition.

-   There is a contiguous substring of $S$ that is a level-$X$ dango string.

If there is no such integer, print `-1`.

### Input

The input is given from Standard Input in the following format:

```
$N$
$S$
```

### Output

Print the greatest positive integer $X$ such that $S$ contains a level-$X$ dango string, or `-1` if there is no such integer.

### Constraints

-   $1\leq N\leq 2\times10^5$
-   $S$ is a string of length $N$ consisting of `o` and `-`.

4

For instance, the substring oooo- corresponding to the 3-rd through 7-th characters of S is a level-4 dango string. No substring of S is a level-5 dango string or above, so you should print 4.

-1

Only the empty string and - are the substrings of S. They are not dango strings, so you should print -1.