1 #include <cstdio>
 2 #include <cstring>
 3 #include <algorithm>
 4 #include <iostream>
 5 #include <queue>
 6 using namespace std;
 7 #define N 105
 8 #define INF 0x3f3f3f3f
 9 
10 struct node
11 {
12     int x, y, t, key, snake;
13     node() {}
14     node(int x, int y, int t, int key, int snake) : x(x), y(y), t(t), key(key), snake(snake) {}
15 };
16 bool vis[N][N][10][40];
17 int n, m, sx, sy, ex, ey;
18 int dx[] = {1, -1, 0, 0}, dy[] = {0, 0, 1, -1};
19 char maze[N][N];
20 
21 bool check(int x, int y)
22 {
23     if(0<=x&&x<n&&0<=y&&y<n&&maze[x][y]!=‘#‘) return true;
24     return false;
25 }
26 
27 void bfs()
28 {
29     int ans = INF;
30     memset(vis, 0, sizeof(vis));
31     queue<node> que;
32     while(!que.empty()) que.pop();
33     que.push(node(sx, sy, 0, 0, 0));
34     while(!que.empty()) {
35         node top = que.front(); que.pop();
36         int x = top.x, y = top.y, key = top.key, snake = top.snake, t = top.t;
37         if(key == m && maze[x][y] == ‘T‘) {
38             ans = min(ans, t);
39         }
40         if(vis[x][y][key][snake] != 0) continue;
41         vis[x][y][key][snake] = 1;
42         for(int i = 0; i < 4; i++) {
43             int nx = x + dx[i], ny = y + dy[i];
44             if(!check(nx, ny)) continue;
45             node now = top;
46             if(‘A‘ <= maze[nx][ny] && maze[nx][ny] <= ‘G‘) {
47                 //只有五条蛇，不能写 <= ‘Z‘
48                 int s = maze[nx][ny] - ‘A‘;
49                 if((1<<s) & now.snake) ; //如果蛇被打了
50                 else {
51                     now.snake |= (1<<s); //没被打
52                     now.t++;
53                 }
54             } else if(maze[nx][ny] - ‘0‘ == now.key + 1) {
55                 now.key++;
56             }
57             now.t++;
58             que.push(node(nx, ny, now.t, now.key, now.snake));
59         }
60     }
61     if(ans != INF) printf("%d\n", ans);
62     else printf("impossible\n");
63 }
64 
65 int main()
66 {
67     while(~scanf("%d%d", &n, &m), n+m) {
68         int cnt = 0;
69         for(int i = 0; i < n; i++) {
70             scanf("%s", maze[i]);
71         }
72         for(int i = 0; i < n; i++) {
73             for(int j = 0; j < n; j++) {
74                 if(maze[i][j] == ‘K‘) sx = i, sy = j;
75                 if(maze[i][j] == ‘S‘) {maze[i][j] = cnt+‘A‘; cnt++;}
76             }
77         }
78         bfs();
79     }
80     return 0;
81 }
82 
83 /*
84 4 2
85 KS1.
86 2SS.
87 SSSS
88 STSS
89 0 0
90 */