#include <iostream>

#include <vector>

#include <string>

using namespace std;

#ifdef WIN32

#define for if(0); else for

#endif

class point {

public:

int x;

int y;

point() {

}

point(int xx, int yy) {

x = xx, y = yy;

}

point &operator = (const point& cc) {

this->x = cc.x;

this->y = cc.y;

return *this;

}

};

int dir[4][2] = {{-1, 0}, {0, 1}, {1, 0}, {0, -1}};

int w, h, board = 0;

void bfs(vector<vector<int> >& mat, point& a, point& b) {

vector<point> queue(10000);

int head, tail, nhead, ntail, step = 0, tx, ty;

head = tail = 0;

queue[0] = a;

while (1) {

++step;

nhead = tail + 1, ntail = tail;

for (int i = head; i <= tail; ++i) {

for (int dd = 0; dd < 4; ++dd) {

tx = queue[i].x, ty = queue[i].y;

while (1) {

tx += dir[dd][0], ty += dir[dd][1];

if (tx < 0 || tx > h + 1 || ty < 0 || ty > w + 1) break;

if (tx == b.x && ty == b.y) {

cout << step << " segments." << endl;

return;

}

if (mat[tx][ty] == -1 || (mat[tx][ty] != 0 && mat[tx][ty] < step)) break;

if (mat[tx][ty] == step) continue;

mat[tx][ty] = step;

queue[++ntail] = point(tx, ty);

}

}

}

if (ntail < nhead) break;

for (int i = nhead; i <= ntail; ++i) {

queue[i - nhead] = queue[i];

}

head = 0, tail = ntail - nhead;

}

cout << "impossible." << endl;

}

void Run() {

vector<vector<int> > mat(h + 2, vector<int>(w + 2, 0));

vector<vector<int> > bak(h + 2, vector<int>(w + 2, 0));

char in[100];

cin.getline(in, 100, '\n');

for (int i = 0; i < h; ++i) {

cin.getline(in, 100, '\n');

for (int j = 0; j < strlen(in); ++j) {

if (in[j] == 'X') mat[i + 1][j + 1] = -1;

}

}

copy(mat.begin(), mat.end(), bak.begin());

cout << "Board #" << ++board << ":" << endl;

point a, b;

int pair = 0;

while (cin >> a.y >> a.x >> b.y >> b.x) {

if (a.x == 0 && a.y == 0 && b.x == 0 && b.y == 0) break;

cout << "Pair " << ++pair << ": ";

copy(bak.begin(), bak.end(), mat.begin());

bfs(mat, a, b);

}

cout << endl;

}

int main() {

while (cin >> w >> h && w + h) {

Run();

}

return 0;

}