using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static string[] SList(long n) => Enumerable.Repeat(0, (int)n).Select(_ => ReadLine()).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var s = SList(n);
        var ans = Count(0, n - 1, 0, n - 1, s);
        if (CanPutHori(0, 0, s) || CanPutHori(0, 1, s)) ans = Math.Max(ans, Count(1, n - 1, 0, n - 1, s) + 1);
        if (CanPutHori(n - 1, 0, s) || CanPutHori(n - 1, 1, s)) ans = Math.Max(ans, Count(0, n - 2, 0, n - 1, s) + 1);
        if (CanPutVert(0, 0, s) || CanPutVert(1, 0, s)) ans = Math.Max(ans, Count(0, n - 1, 1, n - 1, s) + 1);
        if (CanPutVert(0, n - 1, s) || CanPutVert(1, n - 1, s)) ans = Math.Max(ans, Count(0, n - 1, 0, n - 2, s) + 1);
        if (((CanPutHori(0, 0, s) || CanPutHori(0, 1, s)) && CanPutVert(1, 0, s)) || (CanPutHori(0, 1, s) && (CanPutVert(0, 0, s) || CanPutVert(1, 0, s))))
            ans = Math.Max(ans, Count(1, n - 1, 1, n - 1, s) + 2);
        if (((CanPutHori(0, 0, s) || CanPutHori(0, 1, s)) && CanPutVert(1, n - 1, s)) || (CanPutHori(0, 0, s) && (CanPutVert(0, n - 1, s) || CanPutVert(1, n - 1, s))))
            ans = Math.Max(ans, Count(1, n - 1, 0, n - 2, s) + 2);
        if (((CanPutHori(n - 1, 0, s) || CanPutHori(n - 1, 1, s)) && CanPutVert(0, 0, s)) || (CanPutHori(n - 1, 1, s) && (CanPutVert(0, 0, s) || CanPutVert(1, 0, s))))
            ans = Math.Max(ans, Count(0, n - 2, 1, n - 1, s) + 2);
        if (((CanPutHori(n - 1, 0, s) || CanPutHori(n - 1, 1, s)) && CanPutVert(0, n - 1, s)) || (CanPutHori(n - 1, 0, s) && (CanPutVert(0, n - 1, s) || CanPutVert(1, n - 1, s))))
            ans = Math.Max(ans, Count(0, n - 2, 0, n - 2, s) + 2);
        WriteLine(ans);
    }
    static int Count(int xs, int xe, int ys, int ye, string[] s)
    {
        var ans = 0;
        if (ye - ys >= s.Length - 2)
        {
            var sub = 0;
            for (var i = xs; i <= xe; ++i)
            {
                if (ye - ys == s.Length - 1) if (CanPutHori(i, ys, s) || CanPutHori(i, ys + 1, s)) ++sub;
                if (ye - ys == s.Length - 2) if (CanPutHori(i, ys, s)) ++sub;
            }
            ans = Math.Max(ans, sub);
        }
        if (xe - xs >= s.Length - 2)
        {
            var sub = 0;
            for (var j = ys; j <= ye; ++j)
            {
                if (xe - xs == s.Length - 1) if (CanPutVert(xs, j, s) || CanPutVert(xs + 1, j, s)) ++sub;
                if (xe - xs == s.Length - 2) if (CanPutVert(xs, j, s)) ++sub;
            }
            ans = Math.Max(ans, sub);
        }
        return ans;
    }
    static bool CanPutHori(int x, int y, string[] s)
    {
        for (var j = 0; j < s.Length - 1; ++j) if (s[x][y + j] == '#') return false;
        return true;
    }
    static bool CanPutVert(int x, int y, string[] s)
    {
        for (var i = 0; i < s.Length - 1; ++i) if (s[x + i][y] == '#') return false;
        return true;
    }
}