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

namespace CodeForces
{
    class Program
    {
        public static void Main()
        {
            string input = Console.ReadLine();
            int n = Convert.ToInt32(input.Split()[0]);
            int m = Convert.ToInt32(input.Split()[1]);
            int time = 0;
            int startIndex = 0;
            int c = 0;
            int rightStairs = m + 1;
            string[] str = new string[n];
            for (int i = n - 1; i >= 0; i--)
            {
                str[i] = Console.ReadLine();
            }
            for (int i = 0; i < n; i++)
            {
                if (startIndex == 0)
                {
                    int tempTime = time;
                    input = str[i];
                    int indexOfChar = input.IndexOf('1', startIndex);
                    while (indexOfChar != -1)
                    {
                        time += indexOfChar - startIndex;
                        startIndex = indexOfChar + 1;
                        indexOfChar = input.IndexOf('1', startIndex);
                        startIndex--;
                    }
                    if (tempTime == time)
                    {
                        time += -c - 1;
                        break;
                    }
                    else if (i + 1 == n)
                    {
                        break;
                    }
                    if (rightStairs - startIndex < startIndex)
                    {
                        time += rightStairs - startIndex;
                        c = rightStairs - startIndex;
                        startIndex = rightStairs;
                    }
                    else
                    {
                        time += startIndex;
                        c = startIndex;
                        startIndex = 0;
                    }
                    time++;
                }
                else
                {
                    int tempTime = time;
                    input = str[i];
                    int indexOfChar = input.LastIndexOf('1', startIndex);
                    while (indexOfChar != -1)
                    {
                        time += startIndex - indexOfChar;
                        startIndex = indexOfChar - 1;
                        indexOfChar = input.LastIndexOf('1', startIndex);
                        startIndex++;
                    }
                    if (tempTime == time)
                    {
                        time += -c - 1;
                        break;
                    }
                    else if (i + 1 == n)
                    {
                        break;
                    }
                    else if (rightStairs - startIndex < startIndex)
                    {
                        time += rightStairs - startIndex;
                        c = rightStairs - startIndex;
                        startIndex = rightStairs;
                    }
                    else
                    {
                        time += startIndex;
                        c = startIndex;
                        startIndex = 0;
                    }
                    time++;
                }
            }
            if (time != -1)
                Console.WriteLine(time);
            else Console.WriteLine(0);
        }
    }
}