#include <iostream>

#include <string>

#define MAXN 78

#define min _min

#define inf 123456789

using namespace std;

char _m[MAXN][MAXN];

bool mark[MAXN][MAXN];

int dp[MAXN][MAXN];

int dis[][] = {,,,-,,,-,};

int dis_mark[] = {,,,};

int min;

int x_2;

int y_2;

int real_w;

int real_h;

void dfs(int x,int y,int dir,int step);

int main()

{

    //freopen("acm.acm","r",stdin);

//    freopen("out.txt","w",stdout);

    int w;

    int h;

    int i;

    int j;

    int x_1;

    int y_1;

    int temp_x;

    int temp_y;

    string s;

    int time = ;

    while(cin>>w>>h,w||h)

    {

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

        getchar();

        int time_in = ;

        real_w = w+;

        real_h = h+;

        memset(_m,' ',sizeof(_m));

        for(i = ; i <= h; ++ i)

        {

            getline(cin,s);

            for(j = ; j <= w; ++ j)

            {

                _m[i][j] = s[j-];

            }

        }

        while(cin>>y_1>>x_1>>y_2>>x_2,x_1||y_1||x_2||y_2)

        {

            cout<<"Pair "<<++ time_in<<": ";

            memset(mark,false,sizeof(mark));

            for(i = ; i < MAXN; ++ i)

            {

                for(j = ; j < MAXN; ++ j)

                {

                    dp[i][j] = inf;

                }

            }

            min = inf;

            for(i = ; i < ; ++ i)

            {

                temp_x = x_1 + dis[i][];

                temp_y = y_1 + dis[i][];

                if((_m[temp_x][temp_y] != 'X' ||_m[temp_x][temp_y] == 'X' && temp_x == x_2 && temp_y == y_2) && !mark[temp_x][temp_y])

                {

                    mark[temp_x][temp_y] = true;

                    dfs(temp_x,temp_y,dis_mark[i],);

                    mark[temp_x][temp_y] = false;

                }

            }

            if(min == inf)

            {

                cout<<"impossible."<<endl;

            }

            else

            {

                cout<<min;

                cout<<" segments."<<endl;

            }

        }

        cout<<endl;

    }

}

//上 1

//下 2

//左 3

//右 4

void dfs(int x,int y,int dir,int step)

{

    if(x == x_2 && y == y_2)

    {

        if(step < min)

        {

            min = step;

        }

        return;

    }

    if(step < dp[x][y])

    {

        dp[x][y] = step;

    }

    else

    {

        return;

    }

    int i;

    int j;

    int temp_x;

    int temp_y;// 右

    for(i = ; i < ; ++ i)

    {

        temp_x = dis[i][] + x;

        temp_y = dis[i][] + y;

        if(temp_x >=  && temp_x < real_h && temp_y >=  && temp_y <= real_w &&( _m[temp_x][temp_y] != 'X' || _m[temp_x][temp_y] == 'X' && temp_x == x_2 && temp_y == y_2)&& !mark[temp_x][temp_y])

        {

            mark[temp_x][temp_y] = true;

            if(dis_mark[i] != dir)

            {

                dfs(temp_x,temp_y,dis_mark[i],step+);

                if(step+ < dp[temp_x][temp_y])

                    dp[temp_x][temp_y] = step+;

            }

            else

            {

                dfs(temp_x,temp_y,dis_mark[i],step);

                if(step < dp[temp_x][temp_y])

                    dp[temp_x][temp_y] = step;

            }

            mark[temp_x][temp_y] = false;

        }

    }

}