using System;
using System.Collections.Generic;
using System.Linq;

/*******
 * Read input from Console
 * Use Console.WriteLine to output your result.
 * Use:
 *       Utils.LocalPrint( variable);
 * to display simple variables in a dedicated area.
 *
 * Use:
 *
		Utils.LocalPrintArray( collection)
 * to display collections in a dedicated area.
 * ***/

namespace CSharpContestProject
{
    public class Program
    {
        static void Main(string[] args)
        {
            string line;
            var input = new List<string>();
            while ((line = Console.ReadLine()) != null)
            {
                input.Add(line);
            }
            new Problem(input).Solution();
        }
    }

    public class Problem
    {
        private char[][] grid;
        private int N;

        public Problem(List<string> input)
        {
            N = int.Parse(input.First());
            grid = input.Skip(1).Select(l => l.ToArray()).ToArray();
        }

        public void Solution()
        {
            var doorCount = grid.Select(l => l.Count(c => c == 'X')).Sum();
            var travelCount = 0;
            while(doorCount > 0)
            {
                var minColumn = 0;

                foreach (var row in Enumerable.Range(0, N))
                    foreach (var column in Enumerable.Range(minColumn, N - minColumn))
                        if (grid[row][column] == 'X')
                        {
                            grid[row][column] = '.';
                            doorCount--;
                            minColumn = column;
                        }

                travelCount++;
            }
            Console.WriteLine(travelCount);
        }
    }
}