p02114 Fissure Puzzle Easy
Problem

There is a grid of $ N \ times N $ cells. Initially all cells are white. Follow the steps below to increase the number of black squares.

Select one white cell from the cells that are even-numbered from the top and even-numbered from the left. The selected square turns black. Further, the adjacent white squares also change to black in a chain reaction in each of the vertical and horizontal directions of the squares. This chain continues until there are no white cells in that direction. (An example is shown below)

□□□□□□□□□
□□□□□□□□□
□□□□□□□□□
□□□□□□□□□
□□□□□□□□□
□□□□□□□□□
□□□□□□□□□
□□□□□□□□□
□□□□□□□□□
↓ Select the 4th from the top and the 6th from the left
□□□□□ ■ □□□
□□□□□ ■ □□□
□□□□□ ■ □□□
■■■■■■■■■
□□□□□ ■ □□□
□□□□□ ■ □□□
□□□□□ ■ □□□
□□□□□ ■ □□□
□□□□□ ■ □□□
↓ Select the second from the top and the second from the left
□ ■ □□□ ■ □□□
■■■■■■ □□□
□ ■ □□□ ■ □□□
■■■■■■■■■
□□□□□ ■ □□□
□□□□□ ■ □□□
□□□□□ ■ □□□
□□□□□ ■ □□□
□□□□□ ■ □□□
↓ Select 6th from the top and 8th from the left
□ ■ □□□ ■ □□□
■■■■■■ □□□
□ ■ □□□ ■ □□□
■■■■■■■■■
□□□□□ ■ □ ■ □
□□□□□ ■■■■
□□□□□ ■ □ ■ □
□□□□□ ■ □ ■ □
□□□□□ ■ □ ■ □


You want to create a grid where the color of the $ i $ th cell from the top and the $ j $ th cell from the left is $ A_ {i, j} $. Find the minimum number of times to select a square.

Constraints

The input satisfies the following conditions.

* $ 3 \ le N \ le 127 $
* $ N $ is odd
* $ A_ {i, j} $ is'o'or'x'
* Only input that can be made is given

Input

The input is given in the following format.

$ N $
$ A_ {1,1} $ $ A_ {1,2} $ ... $ A_ {1, N} $
$ A_ {2,1} $ $ A_ {2,2} $ ... $ A_ {2, N} $
...
$ A_ {N, 1} $ $ A_ {N, 2} $ ... $ A_ {N, N} $


When $ A_ {i, j} $ is'o', it means that the $ i $ th cell from the top and the $ j $ th cell from the left are white, and when it is'x', it is a black cell. Represents that.

Output

Outputs the minimum number of times to select a cell on the first line.

Examples

Input

5
oxooo
oxooo
oxooo
xxxxx
oxooo


Output

1


Input

9
oxoooooxo
oxxxxxxxx
oxoooooxo
xxxxxxxxx
oxoxooooo
oxxxxxxxx
oxoxoxooo
oxoxxxxxx
oxoxoxooo


Output

4
```python
from collections import deque
n = int(input())
A = [input() for i in range(n)]

cnt = 0
dd = [[-1, 0], [0, -1], [1, 0], [0, 1]]
used = {}
for i in range(n):
    for j in range(n):
        if A[i][j] == 'x' or (i, j) in used:
            continue
        deq = deque([(j, i)])
        used[i, j] = 1
        cnt += 1
        while deq:
            x, y = deq.popleft()
            for dx, dy in dd:
                nx = x + dx; ny = y + dy
                if 0 <= nx < n and 0 <= ny < n:
                    if A[ny][nx] == 'o' and (ny, nx) not in used:
                        used[ny, nx] = 1
                        deq.append((nx, ny))
print(cnt//3)
```