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] + 1)); } } } } } writeln((ans >= INF) ? -1 : ans); } } catch (EOFException e) { } }