#include<iostream>

 #include<cstdio>

 #include<cstring>

 #include<queue>

 #include<algorithm>

 using namespace std;

 const int N=;

 int r,c,sx,sy,ex,ey,ans;

 int vis[N][N],Map[N][N];

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

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

 bool isin(int x,int y)

 {

     return x>=&&x<=r+&&y>=&&y<=c+;

 }

 struct node

 {

     int x,y,s;

 };

 node a,b;

 queue<node> q;

 void BFS()

 {

     int i,j,k,x,y;

     while(!q.empty())

     {

         a=q.front(); q.pop();

         for(k=;k<;k++)

         {

             x=a.x,y=a.y;

             while()

             {

                 x+=dx[k]; y+=dy[k];

                 if(!isin(x,y)) break;

                 if(x==ex&&y==ey){ans=a.s;return ;}

                 if(!vis[x][y])

                 {

                     b.x=x; b.y=y;b.s=a.s+;

                     q.push(b);

                     vis[x][y]=;

                 }

                 else break;

             }

         }

     }

 }

 int main()

 {

     //freopen("test.txt","r",stdin);

     int cas=,t;

     while(scanf("%d%d",&c,&r)!=EOF&&c)

     {

         int i,j;

         char ch[];

         memset(Map,,sizeof(Map));

         gets(ch);

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

         {

             gets(ch);

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

                 if(ch[j]=='X') Map[i][j+]=;

         }

         printf("Board #%d:\n",++cas);

         t=;

         while(scanf("%d%d%d%d",&sy,&sx,&ey,&ex)!=EOF&&sy)

         {

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

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

                     vis[i][j]=Map[i][j];

             while(!q.empty()) q.pop();

             a.x=sx,a.y=sy,a.s=;

             q.push(a);

             ans=-;

             BFS();

             printf("Pair %d: ",++t);

             if(ans==-) printf("impossible.\n");

             else printf("%d segments.\n",ans);

         }

         printf("\n");

     }

     return ;

 }