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 DX = [+1, 0, -1, 0];
enum DY = [0, +1, 0, -1];

enum INF = 10^^9;

void main() {
  try {
    for (; ; ) {
      const H = readInt();
      const W = readInt();
      const SX = readInt() - 1;
      const SY = readInt() - 1;
      const TX = readInt() - 1;
      const TY = readInt() - 1;
      auto A = new char[][H];
      foreach (x; 0 .. H) {
        A[x] = readToken().dup;
      }
      
      alias Pt = Tuple!(int, "x", int, "y");
      auto que = new Pt[H * W];
      int qb, qe;
      auto dist = new int[][](H, W);
      auto prev = new Pt[][](H, W);
      foreach (x; 0 .. H) foreach (y; 0 .. W) {
        dist[x][y] = -1;
      }
      dist[SX][SY] = 0;
      que[qe++] = Pt(SX, SY);
      for (; qb != qe; ) {
        const x = que[qb].x;
        const y = que[qb].y;
        ++qb;
        if (A[x + 1][y] == '.' && dist[x + 1][y] == -1) { dist[x + 1][y] = dist[x][y] + 1; prev[x + 1][y] = Pt(x, y); que[qe++] = Pt(x + 1, y); }
        if (A[x][y + 1] == '.' && dist[x][y + 1] == -1) { dist[x][y + 1] = dist[x][y] + 1; prev[x][y + 1] = Pt(x, y); que[qe++] = Pt(x, y + 1); }
        if (A[x - 1][y] == '.' && dist[x - 1][y] == -1) { dist[x - 1][y] = dist[x][y] + 1; prev[x - 1][y] = Pt(x, y); que[qe++] = Pt(x - 1, y); }
        if (A[x][y - 1] == '.' && dist[x][y - 1] == -1) { dist[x][y - 1] = dist[x][y] + 1; prev[x][y - 1] = Pt(x, y); que[qe++] = Pt(x, y - 1); }
      }
      
      qb = qe = 0;
      auto dist1 = new int[][](H, W);
      foreach (x; 0 .. H) foreach (y; 0 .. W) {
        dist1[x][y] = -1;
      }
      dist1[TX][TY] = 0;
      que[qe++] = Pt(TX, TY);
      for (; qb != qe; ) {
        const x = que[qb].x;
        const y = que[qb].y;
        ++qb;
        if (A[x + 1][y] == '.' && dist1[x + 1][y] == -1) { dist1[x + 1][y] = dist1[x][y] + 1; que[qe++] = Pt(x + 1, y); }
        if (A[x][y + 1] == '.' && dist1[x][y + 1] == -1) { dist1[x][y + 1] = dist1[x][y] + 1; que[qe++] = Pt(x, y + 1); }
        if (A[x - 1][y] == '.' && dist1[x - 1][y] == -1) { dist1[x - 1][y] = dist1[x][y] + 1; que[qe++] = Pt(x - 1, y); }
        if (A[x][y - 1] == '.' && dist1[x][y - 1] == -1) { dist1[x][y - 1] = dist1[x][y] + 1; que[qe++] = Pt(x, y - 1); }
      }
      
      A[SX][SY] = '!';
      qb = qe = 0;
      auto distT = new int[][](H, W);
      foreach (x; 0 .. H) foreach (y; 0 .. W) {
        distT[x][y] = -1;
      }
      distT[TX][TY] = 0;
      que[qe++] = Pt(TX, TY);
      for (; qb != qe; ) {
        const x = que[qb].x;
        const y = que[qb].y;
        ++qb;
        if (A[x + 1][y] == '.' && distT[x + 1][y] == -1) { distT[x + 1][y] = distT[x][y] + 1; que[qe++] = Pt(x + 1, y); }
        if (A[x][y + 1] == '.' && distT[x][y + 1] == -1) { distT[x][y + 1] = distT[x][y] + 1; que[qe++] = Pt(x, y + 1); }
        if (A[x - 1][y] == '.' && distT[x - 1][y] == -1) { distT[x - 1][y] = distT[x][y] + 1; que[qe++] = Pt(x - 1, y); }
        if (A[x][y - 1] == '.' && distT[x][y - 1] == -1) { distT[x][y - 1] = distT[x][y] + 1; que[qe++] = Pt(x, y - 1); }
      }
      A[SX][SY] = '.';
      
      A[TX][TY] = '!';
      qb = qe = 0;
      auto distS = new int[][](H, W);
      foreach (x; 0 .. H) foreach (y; 0 .. W) {
        distS[x][y] = -1;
      }
      distS[SX][SY] = 0;
      que[qe++] = Pt(SX, SY);
      for (; qb != qe; ) {
        const x = que[qb].x;
        const y = que[qb].y;
        ++qb;
        if (A[x + 1][y] == '.' && distS[x + 1][y] == -1) { distS[x + 1][y] = distS[x][y] + 1; que[qe++] = Pt(x + 1, y); }
        if (A[x][y + 1] == '.' && distS[x][y + 1] == -1) { distS[x][y + 1] = distS[x][y] + 1; que[qe++] = Pt(x, y + 1); }
        if (A[x - 1][y] == '.' && distS[x - 1][y] == -1) { distS[x - 1][y] = distS[x][y] + 1; que[qe++] = Pt(x - 1, y); }
        if (A[x][y - 1] == '.' && distS[x][y - 1] == -1) { distS[x][y - 1] = distS[x][y] + 1; que[qe++] = Pt(x, y - 1); }
      }
      A[TX][TY] = '.';
      
      debug {
        writeln("dist = ", dist);
        writeln("dist1 = ", dist1);
        writeln("distS = ", distS);
        writeln("distT = ", distT);
      }
      
      int ans = INF;
      if (dist[TX][TY] != -1) {
        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]) {
            if (distS[x][y] != -1 && distT[x][y] != -1) {
              chmin(ans, dist[TX][TY] + distS[x][y] + distT[x][y]);
            }
          }
        }
        foreach (x; 1 .. H - 1) foreach (y; 1 .. W - 1) {
          if (A[x][y] == '.') {
            int cnt;
            foreach (dir; 0 .. 4) {
              if (A[x + DX[dir]][y + DY[dir]] == '.') {
                ++cnt;
              }
            }
            if (cnt >= 3) {
              if (dist[x][y] != -1 && dist1[x][y] != -1) {
                chmin(ans, 2 * (dist[x][y] + dist1[x][y] + 2));
              }
            }
          }
        }
      }
      writeln((ans >= INF) ? -1 : ans);
    }
  } catch (EOFException e) {
  }
}