#include <iostream>
#include <stdio.h>
#include <string>
#include <queue>
using namespace std;

int w, h;

const int MAXINT = 0x7FFFFFFF;

bool has[100][100] = {0};

void init(){
	for(int i = 0; i < 100; i++){
		for(int j = 0; j < 100; j++){
			has[i][j] = 0;
		}
	}
}

struct pt{
	int x,y;
	pt(int x, int y): x(x), y(y){}
};

struct mp{
	int cs[100][100];
	mp(){
		//cout << 1 << endl;
		for(int i = 0; i < 100; i++){
			for(int j = 0; j < 100; j++){
				cs[i][j] = MAXINT;
			}
		}
	}
};

void jisuan(int x, int y, mp *res){
	queue<pt> bfs;
	bool visited[100][100] = {0};
	int fx[100][100] = {0};
	res->cs[x][y] = 0;
	visited[x][y] = 1;
	int x_ = x-1;
	while(x_ >= 0){
		res->cs[x_][y] = 1;
		visited[x_][y] = 1;
		fx[x_][y] = 1;
		if(has[x_][y]) break;
		bfs.push(pt(x_, y));
		x_--;
	}
	x_ = x+1;
	while(x_ <= w+1){
		res->cs[x_][y] = 1;
		visited[x_][y] = 1;
		fx[x_][y] = 1;
		if(has[x_][y]) break;
		bfs.push(pt(x_, y));
		x_++;
	}
	int y_ = y-1;
	while(y_ >= 0){
		res->cs[x][y_] = 1;
		visited[x][y_] = 1;
		fx[x][y_] = -1;
		if(has[x][y_]) break;
		bfs.push(pt(x, y_));
		y_--;
	}
	y_ = y+1;
	while(y_ <= h+1){
		res->cs[x][y_] = 1;
		visited[x][y_] = 1;
		fx[x][y_] = -1;
		if(has[x][y_]) break;
		bfs.push(pt(x, y_));
		y_++;
	}
	while(!bfs.empty()){
		pt p = bfs.front();
		bfs.pop();
		int xx = p.x, yy = p.y;
		int cs = res->cs[xx][yy];
		if(fx[xx][yy] == 1){
			int yy_ = yy-1;
			while(yy_ >= 0){
				bool acc = 0;
				if(!visited[xx][yy_]){
					visited[xx][yy_] = 1;
					acc = 1;
					res->cs[xx][yy_] = cs+1;
					fx[xx][yy_] = -1;
				}
				if(has[xx][yy_]) break;
				if(acc){
					bfs.push(pt(xx, yy_));
				}
				yy_--;
			}
			yy_ = yy+1;
			while(yy_ <= h+1){
				bool acc = 0;
				if(!visited[xx][yy_]){
					visited[xx][yy_] = 1;
					acc = 1;
					res->cs[xx][yy_] = cs+1;
					fx[xx][yy_] = -1;
				}
				if(has[xx][yy_]) break;
				if(acc){
					bfs.push(pt(xx, yy_));
				}
				yy_++;
			}
		}
		else if(fx[xx][yy] == -1){
			int xx_ = xx-1;
			while(xx_ >= 0){
				bool acc = 0;
				if(!visited[xx_][yy]){
					visited[xx_][yy] = 1;
					acc = 1;
					res->cs[xx_][yy] = cs+1;
					fx[xx_][yy] = 1;
				}
				if(has[xx_][yy]) break;
				if(acc){
					bfs.push(pt(xx_, yy));
				}
				xx_--;
			}
			xx_ = xx+1;
			while(xx_ <= w+1){
				bool acc = 0;
				if(!visited[xx_][yy]){
					visited[xx_][yy] = 1;
					acc = 1;
					res->cs[xx_][yy] = cs+1;
					fx[xx_][yy] = 1;
				}
				if(has[xx_][yy]) break;
				if(acc){
					bfs.push(pt(xx_, yy));
				}
				xx_++;
			}
		}
	}
}

int main() {
	int cnt = 1;
	while(1){
		init();
		cin >> w >> h;
		if(w == 0 && h == 0) return 0;
		printf("Board #%d:\n", cnt);
		cnt++;
		string s;
		for(int j = 1; j <= h; j++){
			s = "";
			while(s.length() == 0) getline(cin, s);
			//cout << s << endl;
			for(int i = 1; i <= w; i++){
				char c = s[i-1];
				if(c == 'X') has[i][j] = 1;
			}
		}
		//cout << 1 << endl;
		mp* rcd[100][100] = {{NULL}};
		int ct = 1;
		while(1){
			int x1,y1,x2,y2;
			cin >> x1 >> y1 >> x2 >> y2;
			if(x1==0 && x2==0 && y1==0 && y2==0) break;
			printf("Pair %d: ", ct);
			//cout << "Pair " << ct << ": " << endl;
			ct++;
			//cout << x1 << " " << y1 << endl;
			//cout << rcd[x1][y1] << endl;
			//cout << 4 << endl;
			if(rcd[x1][y1] != NULL){

				//cout << 1 << endl;

				int jg = rcd[x1][y1]->cs[x2][y2];
				if(jg == MAXINT) printf("impossible.\n");
				else printf("%d segments.\n", jg);

			}
			else if(rcd[x2][y2] != NULL){

				//cout << 2 << endl;

				int jg = rcd[x2][y2]->cs[x1][y1];
				if(jg == MAXINT) printf("impossible.\n");
				else printf("%d segments.\n", jg);

			}
			else{
				//cout << 0 << endl;

				rcd[x1][y1] = new mp();
				jisuan(x1, y1, rcd[x1][y1]);
				int jg = rcd[x1][y1]->cs[x2][y2];
				if(jg == MAXINT) printf("impossible.\n");
				else printf("%d segments.\n", jg);

			}
		}
		printf("\n");
	}
	return 0;
}