#include<stdio.h>
#include<string.h>
#include<ctype.h>
char map[110][110];
int istop(int sx,int sy,char x);        //判断是否为表层对话框函数
int main()
{int n,m,i,j,list[26],k,c;while(scanf("%d%d",&n,&m),n+m != 0){memset(list,0,sizeof(list));for(i=1;i<=n;i++){for(j=1;j<=m;j++){scanf(" %c",&map[i][j]);if(isalpha(map[i][j]))list[map[i][j]-'A']=1;//标记有哪些字母标号的对话框出现
            }}for(i=0;i<26;i++){if(list[i]){for(j=1;j<=n;j++){int flag=0;for(k=1;k<=m;k++){if(map[j][k]-'A'==i){list[i]=istop(j,k,map[j][k]);flag=1;break;}}if(flag)break;}}}for(i=0;i<26;i++){if(list[i])printf("%c",'A'+i);}printf("\n");        }return 0;
}
int istop(int sx,int sy,char x)
{int i,j,r,c;i=sx;j=sy+1;while(map[i][j] == x)j++;j--;c=j;//记录该对话框的列数 if(map[i+1][j] != x)return 0;while(map[i][j] == x)i++;    i--;r=i;//记录该对话框的行数 if(map[i][j-1]!=x)return 0;while(map[i][j] == x)j--;    j++;if(map[i-1][j]!=x)return 0;while(map[i][j] == x)i--;    i++;if(i!=sx &&j!=sy)return 0;for(i=sx+1;i<r;i++)//判断该对话框内是否有嵌套对话框 for(j=sy+1;j<c;j++)if(map[i][j]!='.')return 0;return 1;
}

 1 #include<stdio.h>
 2 #include<string.h>
 3 #include<ctype.h>
 4 char map[110][110];
 5 int istop(int sx,int sy,char x);
 6 int main()
 7 {
 8     int n,m,i,j,list[26],k,c;
 9     while(scanf("%d%d",&n,&m),n+m != 0)
10     {
11         memset(list,0,sizeof(list));
12         for(i=1;i<=n;i++)
13         {
14             for(j=1;j<=m;j++)
15             {
16                 scanf(" %c",&map[i][j]);
17                 if(isalpha(map[i][j]))
18                 list[map[i][j]-'A']=1;
19             }
20         }
21         for(i=0;i<26;i++)
22         {
23             if(list[i])
24             {
25                 for(j=1;j<=n;j++)
26                 {
27                     int flag=0;
28                     for(k=1;k<=m;k++)
29                     {
30                         if(map[j][k]-'A'==i)
31                         {
32                             list[i]=istop(j,k,map[j][k]);
33                             flag=1;
34                             break;
35                         }
36                     }
37                     if(flag)
38                     break;
39                 }
40             }
41         }
42         for(i=0;i<26;i++)
43         {
44             if(list[i])
45                 printf("%c",'A'+i);
46         }
47         printf("\n");
48     }
49     return 0;
50 }
51 int istop(int sx,int sy,char x)
52 {
53     int i,j,r,c;
54     i=sx;
55     j=sy+1;
56     while(map[i][j] == x)
57     j++;
58     j--;
59     c=j;
60     if(map[i+1][j] != x)
61     return 0;
62
63     while(map[i][j] == x)
64     i++;
65     i--;
66     r=i;
67     if(map[i][j-1]!=x)
68     return 0;
69
70     while(map[i][j] == x)
71     j--;
72     j++;
73     if(map[i-1][j]!=x)
74     return 0;
75
76     while(map[i][j] == x)
77     i--;
78     i++;
79     if(i!=sx &&j!=sy)
80     return 0;
81
82     for(i=sx+1;i<r;i++)
83         for(j=sy+1;j<c;j++)
84             if(map[i][j]!='.')
85             return 0;
86