1 #include<cstdio>
2 #include<algorithm>
3 #include<cstring>
4 #include<vector>
5 #include<queue>
6 #define N 400
7 using namespace std;
8 int t,n,m,dis[N][N],vis[N],dx[5]={1,0,-1,0};
9 int dy[5]={0,1,0,-1};
10 int d_cnt,ans,adj[N][N],V[N],live,tot,bf[N];
11 char mp[N][N];
12 queue <int> qx,qy;
13 inline int get(int x,int y) {return m*(x-1)+y;}
14 void add(int T)
15 {
16 for (int i=1;i<=n;i++)
17 for (int j=1;j<=m;j++)
18 for (int k=1;k<=d_cnt;k++)
19 if (mp[i][j]=='.' && dis[k][get(i,j)]<=T)
20 adj[k][get(i,j)]=1;
21 }
22 void BFS(int X,int Y)
23 {
24 ++d_cnt;
25 qx.push(X),qy.push(Y);
26 memset(vis,-1,sizeof(vis));
27 vis[get(X,Y)]=0;
28 while (!qx.empty())
29 {
30 int x=qx.front(),y=qy.front();
31 for (int i=0;i<4;i++)
32 {
33 int xx=x+dx[i],yy=y+dy[i];
34 if (mp[xx][yy]=='.' && vis[get(xx,yy)]==-1)
35 {
36 qx.push(xx),qy.push(yy);
37 vis[get(xx,yy)]=vis[get(x,y)]+1;
38 dis[d_cnt][get(xx,yy)]=vis[get(xx,yy)];
39 }
40 }
41 qx.pop(),qy.pop();
42 }
43 }
44 int find(int x)
45 {
46 for (int i=1;i<=n*m;i++)
47 {
48 if (!V[i] && adj[x][i]==1)
49 {
50 V[i]=1;
51 if (!bf[i] || find(bf[i]))
52 {
53 bf[i]=x;
54 return 1;
55 }
56 }
57 }
58 return 0;
59 }
60 void init()
61 {
62 memset(dis,127,sizeof(dis));
63 memset(adj,0,sizeof(adj));
64 memset(bf,0,sizeof(bf));
65 d_cnt=0;
66 live=0;
67 ans=0;
68 }
69 int main()
70 {
71 scanf("%d",&t);
72 while (t--)
73 {
74 init();
75 scanf("%d%d",&n,&m);
76 for (int i=1;i<=n;i++)
77 scanf("%s",mp[i]+1);
78 for (int i=1;i<=n;i++)
79 for (int j=1;j<=m;j++)
80 if (mp[i][j]=='D')
81 BFS(i,j);
82 else if (mp[i][j]=='.') live++;
83 for (int k=1;k<=150;k++)
84 {
85 add(k);
86 for (int i=1;i<=d_cnt;i++)
87 {
88 memset(V,0,sizeof(V));
89 if (find(i)) ans++;
90 }
91 if (ans==live)
92 {
93 printf("%d\n",k);
94 break;
95 }
96 }
97 if (ans!=live)
98 puts("impossible");
99 }
100 return 0;
101 }
