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 -.

Sample Input 1

10
o-oooo---o

Sample Output 1

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.

Sample Input 2

1

Sample Output 2

-1

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

Sample Input 3

30
-o-o-oooo-oo-o-ooooooo--oooo-o

Sample Output 3

7

见题面 Input 部分

见题面 Output 部分