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;

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 string[H];
      foreach (x; 0 .. H) {
        A[x] = readToken;
      }
      
      auto mx = new int[][](H, W);
      foreach (x; 0 .. H) {
        if (x == 0) {
          mx[x][] = -1;
        } else {
          mx[x][] = mx[x - 1][];
        }
        foreach (y; 0 .. W) if (A[x][y] == '.') {
          mx[x][y] = x;
        }
      }
      
      DList!int que;
      auto dist = new int[][](H, W);
      foreach (x; 0 .. H) {
        dist[x][] = INF;
      }
      dist[SX][SY] = 0;
      que.insertBack(SX * W + SY);
      auto vis = new bool[][](H, W);
      auto fs = new int[W];
      auto gss = new int[][](2, W);
      
      for (; !que.empty; ) {
        const x = que.front / W;
        const y = que.front % W;
        que.removeFront;
        void update(int t, int xx, int yy) {
          if (A[xx][yy] == '.') {
            if (chmin(dist[xx][yy], dist[x][y] + t)) {
              if (t) {
                que.insertBack(xx * W + yy);
              } else {
                que.insertFront(xx * W + yy);
              }
            }
          }
        }
        if (!vis[x][y]) {
          debug {
            writeln(dist[x][y], " ", x, " ", y);
          }
          vis[x][y] = true;
          foreach (yy; [y - 1, y + 1]) if (0 <= yy && yy < W) {
            const limX = min(x + 1, H - 1);
            for (; fs[yy] <= limX; ++fs[yy]) {
              update(0, fs[yy], yy);
            }
          }
          foreach (t; 0 .. 2) {
            foreach (yy; [y - 1, y + 1]) if (0 <= yy && yy < W) {
              const xx = mx[x][yy];
              if (~xx) {
                const energy = x - xx;
                const limX = min(xx + 1 + (t ? energy : (energy / 2)), H - 1);
                foreach (yyy; [yy - 1, yy + 1]) if (0 <= yyy && yyy < W) {
                  for (; gss[t][yyy] <= limX; ++gss[t][yyy]) {
                    update(t, gss[t][yyy], yyy);
                  }
                }
              }
            }
          }
        }
      }
      
      const ans = dist[TX][TY];
      writeln((ans >= INF) ? -1 : ans);
    }
  } catch (EOFException e) {
  }
}