#!/usr/bin/ python3.8
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
import numpy as np

N = int(readline())
S = np.frombuffer(read(), 'S1').reshape(N, -1)[:, :N].copy()


def solve_vertical(S):
    H, W = S.shape
    cond_1 = np.all(S[:-1] == b'.', axis=0)
    cond_2 = np.all(S[1:] == b'.', axis=0)
    return np.count_nonzero(cond_1 | cond_2)


def solve(S):
    yield solve_vertical(S)
    yield solve_vertical(S.T)
    for _ in range(2):
        S = S.T
        for _ in range(4):
            S = S[::-1].T
            if np.all(S[0, 1:] == b'.'):
                S[0, 1:] = b'#'
                for x in solve(S):
                    yield x + 1


print(max(solve(S)))