var read = require('readline').createInterface({
  input: process.stdin,
  output: process.stdout
});
var obj;
var inLine = [];
read.on('line', function(input){inLine.push(input);});
read.on('close', function(){
  obj = init(inLine);
  myerr("-----start-----");
  var start = new Date();
  Main();
  var end = new Date() - start;
  myerr("----- end -----");
  myerr("time : " + (end) + "ms");
});
function nextInt(){return myconv(next(),1);} function nextStrArray(){return myconv(next(),2);}
function nextIntArray(){return myconv(next(),4);} function nextCharArray(){return myconv(next(),6);}
function next(){return obj.next();} function hasNext(){return obj.hasNext();}
function init(input){  
  var returnObj = {
    list : input, index : 0, max : input.length,
    hasNext : function(){return (this.index < this.max);},
    next : function(){if(!this.hasNext()){throw "ArrayIndexOutOfBoundsException これ以上ないよ";}else{var returnInput = this.list[this.index];this.index++;return returnInput;}}
  };
  return returnObj;
}
function myout(s){console.log(s);}
function myerr(s){console.error("debug:" + require("util").inspect(s,false,null));}
//[no]要素の扱い。数値型
//不明値、異常時:引数そのまま返す 1:数値へ変換
//2:半角SPで分割 4:半角SPで分割し、数値配列へ
//6:1文字で分割  7:1文字で分割し、数値配列へ
//8:半角SPで結合 9:改行で結合 0:文字なしで結合
function myconv(i,no){try{switch(no){case 1:return parseInt(i);case 2:return i.split(" ");case 4:return i.split(" ").map(Number);case 6:return i.split("");case 7:return i.split("").map(Number);case 8:return i.join(" ");case 9:return i.join("\n");case 0:return i.join("");default:return i;}}catch(e){return i;}}
function Main(){
       var one = nextIntArray();
  var R = one[0];
  var C = one[1];
  var s = nextIntArray();//y,x
  s = {
    y:s[0] - 1,
    x:s[1] - 1
  };
  var g = nextIntArray();//y,x
  g = {
    y:g[0] - 1,
    x:g[1] - 1
  };
  var list = new Array(R);
  for(var i = 0; i < R; i++){
    list[i] = nextCharArray();
  }
  list[s["y"]][s["x"]] = 0;
  var queue = [[s["y"],s["x"]]];
  var dy = [-1,0,1,0];
  var dx = [0,-1,0,1];
  while(queue.length > 0){
     var tmp = queue.shift();
     for(var i = 0; i < dy.length; i++){
       var nextY = tmp[0] + dy[i];
       var nextX = tmp[1] + dx[i];
       if(nextY < R && nextY >= 0 && nextX >= 0 && nextX < C){
       	  if(list[nextY][nextX] == "."){
            list[nextY][nextX] = list[tmp[0]][tmp[1]] + 1;
            queue.push([nextY,nextX]);
          }
       }
     }
  }
  myout(list[g["y"]][g["x"]]); 
}