http://acm.hdu.edu.cn/showproblem.php?pid=1429
// 1329152 2009-05-02 08:34:49 Accepted 1429 687MS 4252K 2405 B C++ no way 
#include < iostream >
#include < queue >
using   namespace  std;
 struct  Node
 {
    int x;
    int y;
    int step;
    int num;
    bool mark[10];
} ;
 int  dir[ 4 ][ 2 ] = {-1,0,1,0,0,-1,0,1} ;
 int  binary[ 26 ] = {1,2,4,8,16,32,64,128,256,512,1024,2048,4096,8192,16384,32768,65536,131072,
                   262144,524288,1048576,2097152,4194304,8388608,16777216,33554432} ;
 char  gra[ 21 ][ 21 ];
 int  flag[ 21 ][ 21 ][ 2049 ];
 int  m,n,t;
 int  sx,sy,ex,ey;

 void  bfs()
 {
    int i,k,temp,ch;
    Node p,q;
    queue<Node>Q;
    p.x = sx;
    p.y = sy;
    p.step = 0;
    p.num = 0;
    for(i=0;i<10;i++)
        p.mark[i] = false;
    Q.push(p);
    while(!Q.empty())
    {
        q = Q.front();
        Q.pop();
        if(q.x == ex && q.y == ey)
        {
            if(q.step < t)
            {
                cout<<q.step<<endl;
                return ;
            }
            break ;
        }
        for(k=0;k<4;k++)
        {
            p = q;
            p.x += dir[k][0];
            p.y += dir[k][1];
            
            if(p.x >=0 && p.x<m && p.y>=0 && p.y<n && gra[p.x][p.y] != '*')
            {
                if(gra[p.x][p.y] >= 'a' && gra[p.x][p.y] <= 'j')
                {
                    ch = gra[p.x][p.y] - 'a';
                    if(p.mark[ch] == false)
                        temp = p.num + binary[ch];
                    else
                        temp = p.num;
                    if(flag[p.x][p.y][temp] == -1)
                    {
                        flag[p.x][p.y][temp] = q.step + 1;
                        p.step = q.step + 1;
                        p.num = temp;
                        p.mark[ch] = true;
                        Q.push(p);
                    }
                }
                else if(gra[p.x][p.y] >= 'A' && gra[p.x][p.y] <= 'J')
                {
                    ch = gra[p.x][p.y] - 'A';
                    if(flag[p.x][p.y][p.num] == -1 && p.mark[ch] == true)
                    {
                        flag[p.x][p.y][p.num] = q.step + 1;
                        p.step = q.step + 1;
                        Q.push(p);
                    }
                }
                else 
                {
                    if(flag[p.x][p.y][p.num] == -1)
                    {
                        flag[p.x][p.y][p.num] = q.step + 1;
                        p.step = q.step + 1;
                        Q.push(p);
                    }
                }
            }
        }//for(k=0;k<4;k++)
    }//while(!Q.empty())
    cout<<-1<<endl;
}

int  main()
 {
   int i,j,k;
   while(cin>>m>>n>>t)
   {
       for(i=0;i<m;i++)
       {
           scanf("%s",gra[i]);
           for(j=0;j<n;j++)
           {
               if(gra[i][j] == '@')
               {
                   sx = i;
                   sy = j;
               }
               else if(gra[i][j] == '^')
               {
                   ex = i;
                   ey = j;
               }
               for(k=0;k<2049;k++)
                   flag[i][j][k] = -1;
           }
       }
       bfs();
   }
   return 0;
}