Inserting 'x'

We have a string s consisting of lowercase English letters. Snuke can perform the following operation repeatedly:

• Insert a letter x to any position in s of his choice, including the beginning and end of s.

Snuke's objective is to turn s into a palindrome. Determine whether the objective is achievable. If it is achievable, find the minimum number of operations required.

Constraints

• 1 \leq |s| \leq 10^5
• s consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

s

Output

If the objective is achievable, print the number of operations required. If it is not, print -1 instead.

Examples

Input

xabxa

Output

2

Input

ab

Output

-1

Input

a

Output

0

Input

oxxx

Output

3

inputFormat

Input

Input is given from Standard Input in the following format:

s

outputFormat

Output

If the objective is achievable, print the number of operations required. If it is not, print -1 instead.

Examples

Input

xabxa

Output

2

Input

ab

Output

-1

Input

a

Output

0

Input

oxxx

Output

3

样例

a

0