#include <iostream>#include <stdio.h>#include <queue>using namespace std;int dir[4][2] = {-1,0,1,0,0,-1,0,1};int h,w,bx[21],by[21],k;//区域的高和宽，k:守卫人员的位置个数char map[101][101];int mark[101][101];typedef struct{int bodx[21],body[21],steps;}node;node pre,cur;queue<node> q;bool judge(node a)//擒获返回true,否则返回false{for(int j = 0; j < k; j++)    {if(map[a.bodx[j]][a.body[j]]=='Q')return true;    }return false;}node changedirec(node a,int x,int y){for(int j = 0; j < k; j++)    {        a.bodx[j] = a.bodx[j] + x;        a.body[j] = a.body[j] + y;    }return a;}

bool if_over(node a)//判断该位置是否走过，如果没走过那么返回false,如果走过那么返回true{if(mark[a.bodx[0]][a.body[0]]==0)return false;else return true;}bool J_ifCanGo(node a) //如果不能走那么就返回false，能走就返回true。{for(int j = 0; j < k; j++)    {if(a.bodx[j]<1||a.bodx[j]>h||a.body[j]<1||a.body[j]>w||map[a.bodx[j]][a.body[j]]=='O')return false;    }return true;}void set_over(node a){    mark[a.bodx[0]][a.body[0]] = 1;}void bfs(){int i;    pre.steps = 0;for(i = 0; i < k ; i++)    {        pre.bodx[i] = bx[i];        pre.body[i] = by[i];    }while(!q.empty())q.pop();    q.push(pre);    set_over(pre);while(!q.empty())    {        pre = q.front();        q.pop();if(judge(pre))        {            printf("%d\n",pre.steps);return;        }for(i = 0; i < 4; i++)        {            cur = changedirec(pre,dir[i][0],dir[i][1]);            cur.steps = pre.steps + 1;if(J_ifCanGo(cur))            {if(!if_over(cur))                {                    set_over(cur);                    q.push(cur);                }            }        }    }    printf("Impossible\n");}int main(){while(scanf("%d%d",&h,&w))    {if(h==0&&w==0)break;        k = 0;for(int i = 1; i <= h; i++)        {            getchar();for(int j = 1; j <= w; j++)            {                mark[i][j] = 0;                scanf("%c",&map[i][j]);if(map[i][j]=='D')                {                    bx[k] = i;                    by[k] = j;                    k++;                }            }        }

        bfs();    }return 0;}