import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }


enum INF = 10^^9 / 2;

int H, W, SX, SY, TX, TY;
string[] A;

alias Pt = Tuple!(int, "x", int, "y");
Pt[] que;
Tuple!(int[][], Pt[][]) bfs(bool needPrev)(int sx, int sy, int ox, int oy) {
  int qb, qe;
  auto dist = new int[][](H, W);
  Pt[][] prev;
  static if (needPrev) prev = new Pt[][](H, W);
  foreach (x; 0 .. H) foreach (y; 0 .. W) {
    dist[x][y] = INF;
  }
  dist[sx][sy] = 0;
  que[qe++] = Pt(sx, sy);
  for (; qb != qe; ) {
    const x = que[qb].x;
    const y = que[qb].y;
    ++qb;
    void update(int xx, int yy) {
      if (A[xx][yy] == '.' && !(xx == ox && yy == oy)) {
        if (chmin(dist[xx][yy], dist[x][y] + 1)) {
          static if (needPrev) prev[xx][yy] = Pt(x, y);
          que[qe++] = Pt(xx, yy);
        }
      }
    }
    update(x + 1, y);
    update(x, y + 1);
    update(x - 1, y);
    update(x, y - 1);
  }
  return tuple(dist, prev);
}

void main() {
  try {
    for (; ; ) {
      H = readInt();
      W = readInt();
      SX = readInt() - 1;
      SY = readInt() - 1;
      TX = readInt() - 1;
      TY = readInt() - 1;
      A = new string[H];
      foreach (x; 0 .. H) {
        A[x] = readToken();
      }
      
      que = new Pt[H * W];
      const res = bfs!true(SX, SY, -1, -1);
      const dS = res[0];
      const prev = res[1];
      const dT = bfs!false(TX, TY, -1, -1)[0];
      const dST = bfs!false(SX, SY, TX, TY)[0];
      const dTS = bfs!false(TX, TY, SX, SY)[0];
      
      int ans = INF;
      if (dS[TX][TY] < INF) {
        auto on = new bool[][](H, W);
        for (int x = TX, y = TY; ; ) {
          on[x][y] = true;
          if (x == SX && y == SY) {
            break;
          }
          const p = prev[x][y];
          x = p.x;
          y = p.y;
        }
        foreach (x; 1 .. H - 1) foreach (y; 1 .. W - 1) {
          if (A[x][y] == '.' && !on[x][y]) {
            chmin(ans, dS[TX][TY] + dST[x][y] + dTS[x][y]);
          }
        }
        foreach (x; 1 .. H - 1) foreach (y; 1 .. W - 1) {
          if (A[x][y] == '.') {
            int cnt;
            if (A[x + 1][y] == '.') ++cnt;
            if (A[x][y + 1] == '.') ++cnt;
            if (A[x - 1][y] == '.') ++cnt;
            if (A[x][y - 1] == '.') ++cnt;
            if (cnt >= 3) {
              chmin(ans, 2 * (dS[x][y] + dT[x][y] + 2));
            }
          }
        }
      }
      
      writeln((ans >= INF) ? -1 : ans);
    }
  } catch (EOFException e) {
  }
}