using System;
using System.IO;
using System.Linq;
using System.Collections.Generic;
using System.Text;

public class Program
{

    public void Proc()
    {
        this.N = int.Parse(Reader.ReadLine());
        bool[][] map = new bool[this.N][];
        for (int i = 0; i < this.N; i++) {
            map[i] = Reader.ReadLine().Select(a => a == '.').ToArray();
        }

        int ans = GetAns(map);

        bool[][] tateyoko = new bool[this.N][];
        for (int i = 0; i < this.N; i++) {
            tateyoko[i] = new bool[this.N];
            for (int j = 0; j < this.N; j++) {
                tateyoko[i][j] = map[j][i];
            }
        }
        ans = Math.Max(ans, GetAns(tateyoko));

        bool gaisyu = true;
        for (int i = 0; i < this.N; i++) {
            if(!map[i][0]) {
                gaisyu = false;
                break;
            }
            if(!map[i].Last()) {
                gaisyu = false;
                break;
            }
            if(!map[0][i]) {
                gaisyu = false;
                break;
            }
            if(!map.Last()[i]) {
                gaisyu = false;
                break;
            }
        }
        if(gaisyu) {
            ans = Math.Max(ans, 4);
        }
        Console.WriteLine(ans);
    }

    private int GetAns(bool[][] map) {
        int ans = 0;

        int cnt = 0;
        for (int i = 0; i < this.N; i++) {
            if(map[i].Take(this.N-1).All(a=>a)) {
                cnt++;
            }
        }
        if(map.Select(a=>a.Last()).All(a=>a)) {
            cnt++;
        }
        ans = Math.Max(ans, cnt);
        cnt = 0;
        for (int i = 0; i < this.N; i++) {
            if(map[i].Skip(1).All(a=>a)) {
                cnt++;
            }
        }
        if(map.Select(a=>a.First()).All(a=>a)) {
            cnt++;
        }
        ans = Math.Max(ans, cnt);
        cnt = 0;
        for (int i = 0; i < this.N; i++) {
            if(map[i].Take(this.N-1).All(a=>a)||map[i].Skip(1).All(a=>a)) {
                cnt++;
            }
        }
        ans = Math.Max(ans, cnt);
        return ans;
    }


    private int N;

    public class Reader
    {
        private static StringReader sr;
        public static bool IsDebug = false;
        public static string ReadLine()
        {
            if (IsDebug)
            {
                if (sr == null)
                {
                    sr = new StringReader(InputText.Trim());
                }
                return sr.ReadLine();
            }
            else
            {
                return Console.ReadLine();
            }
        }
        private static string InputText = @"



5
...#.
..#.#
.....
#....
##..#





";
    }

    public static void Main(string[] args)
    {
#if DEBUG
        Reader.IsDebug = true;
#endif
        Program prg = new Program();
        prg.Proc();
    }
}