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]; 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(); } alias Pt = Tuple!(int, "x", int, "y"); DList!Pt que; 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 ~= Pt(SX, SY); for (; !que.empty; ) { const x = que.front.x; const y = que.front.y; que.removeFront; foreach (dir; 0 .. 4) { const xx = x + DX[dir]; const yy = y + DY[dir]; if (A[xx][yy] == '.') { if (dist[xx][yy] == -1) { dist[xx][yy] = dist[x][y] + 1; prev[xx][yy] = Pt(x, y); que ~= Pt(xx, yy); } } } } auto distT = new int[][](H, W); foreach (x; 0 .. H) foreach (y; 0 .. W) { distT[x][y] = -1; } distT[TX][TY] = 0; que ~= Pt(TX, TY); for (; !que.empty; ) { const x = que.front.x; const y = que.front.y; que.removeFront; foreach (dir; 0 .. 4) { const xx = x + DX[dir]; const yy = y + DY[dir]; if (A[xx][yy] == '.') { if (distT[xx][yy] == -1) { distT[xx][yy] = distT[x][y] + 1; que ~= Pt(xx, yy); } } } } int ans; 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; } bool good; foreach (x; 1 .. H - 1) foreach (y; 1 .. W - 1) { if (A[x][y] == '.' && !on[x][y]) { if (dist[TX][TY] == dist[x][y] + distT[x][y]) { good = true; } } } if (good) { ans = 2 * dist[TX][TY]; } else { bool ok; foreach (x; 1 .. H - 1) foreach (y; 1 .. W - 1) { if (on[x][y] && !(x == SX && y == SY) && !(x == TX && y == TY)) { foreach (dir; 0 .. 4) { const xx = x + DX[dir]; const yy = y + DY[dir]; if (A[xx][yy] == '.' && !on[xx][yy]) { ok = true; } } } } if (ok) { ans = 2 * dist[TX][TY] + 2; } else { ans = -1; } } } else { ans = -1; } writeln(ans); } } catch (EOFException e) { } }