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

namespace _707
{
    class Program
    {
        static void Main(string[] args)
        {
            var line = Console.ReadLine().Split(' ').Select(int.Parse).ToList();
            var h = line[0];
            var w = line[1];

            var blacks = new List<Tuple<int, int>>();
            for (int x = 0; x < h; x++)
            {
                var row = Console.ReadLine().Select(ch => ch - '0').ToList();
                for (int y = 0; y < w; y++)
                {
                    if (row[y] == 1)
                    {
                        blacks.Add(Tuple.Create(x + 1, y + 1));
                    }
                }
            }

            var positions = Enumerable.Range(0, h + 2)
                                      .SelectMany(x => Enumerable.Range(0, w + 2).Select(y => Tuple.Create(x, y)))
                                      .Where(position => position.Item1 == 0 || position.Item2 == h + 1 || position.Item2 == 0 || position.Item2 == w + 1)
                                      .ToList();

            var answer = positions.Min(position =>
            {
                return blacks.Sum(black =>
                {
                    var x = Math.Pow((double)(position.Item1 - black.Item1), 2.0);
                    var y = Math.Pow((double)(position.Item2 - black.Item2), 2.0);
                    return Math.Sqrt(x + y);
                });
            });
            Console.WriteLine(Math.Round(answer, 8));
        }
    }
}