1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<cmath>
 5 #include<algorithm>
 6 #include<queue>
 7 using namespace std;
 8 struct Node{
 9     int nx,ny,step;
10     //int key[11];
11     int key;
12 };
13 char mp[25][25];
14 int vis[25][25][1025];
15 int disx[4] = {0,0,1,-1};
16 int disy[4] = {1,-1,0,0};
17 int n,m,t;
18 void bfs(int sx,int sy){
19     memset(vis,0,sizeof(vis));
20     queue<Node>q;
21     Node a,b;
22     a.nx = sx;a.ny = sy;
23     a.step = 0;
24     //for(int i = 0;i < 11;i++)a.key[i] = 0;
25     a.key = 0;
26     vis[sx][sy][0] = 1;
27     q.push(a);
28     while(!q.empty()){
29         a = q.front();
30         q.pop();
31         for(int i = 0; i < 4;i++){
32             b.nx = a.nx + disx[i];
33             b.ny = a.ny + disy[i];
34             b.step = a.step + 1;
35             int x = b.nx, y = b.ny, step = b.step;
36             //for(int i = 0;i < 11;i++)b.key[i] = a.key[i];    
37             b.key = a.key;
38             if(x < 0 || y < 0 || x >= n || y >= m)continue;
39             if(mp[x][y] == ‘*‘)continue;
40             if(step >= t)continue;
41             if(mp[x][y] == ‘^‘){
42                 printf("%d\n",step);
43                 return;
44             }
45     //        if(vis[x][y] > 10)continue;
46             if(mp[x][y] >= ‘a‘ && mp[x][y] <= ‘j‘){
47                 //b.key[mp[x][y] - ‘a‘] = 1;
48                 int p = 1 << (mp[x][y] - ‘a‘);
49                 b.key |= p;
50                 if(!vis[x][y][b.key]){
51                     vis[x][y][b.key] = 1;
52                     q.push(b);
53                 }
54                 continue;
55             }
56             if(mp[x][y] >= ‘A‘ && mp[x][y] <= ‘J‘){
57                 //if(b.key[mp[x][y] - ‘A‘] == 0)continue;
58                 int p = 1 << (mp[x][y] - ‘A‘);
59                 if(b.key & p){
60                     if(!vis[x][y][b.key]){
61                         vis[x][y][b.key] = 1;
62                         q.push(b);
63                     }
64                 }
65                 continue;
66             }
67             if(!vis[x][y][b.key]){
68                 vis[x][y][b.key] = 1;
69                 q.push(b);
70             }
71         }
72     }
73     puts("-1");
74     return;
75 }
76 int main(){
77     while(~scanf("%d%d%d",&n,&m,&t)){
78         int sx,sy;
79         for(int i = 0;i < n; i++){
80             scanf("%s",mp[i]);
81             for(int j = 0;j < m; j++){
82                 if(mp[i][j] == ‘@‘){
83                     sx = i;
84                     sy = j;
85                 }
86             }
87         }
88         mp[sx][sy] = ‘.‘;
89         bfs(sx,sy);
90     }
91     return 0;
92 }