#include <iostream>

 #include <queue>

 #include <cstring>

 #include <cstdio>

 using namespace std;

 typedef struct node_st {

     int x, y, t;

     int key;

     node_st() {}

     node_st(int xx, int yy, int tt, int kk) {

         x = xx; y = yy; t = tt; key = kk;

     }

 } node_st;

 char map[][];

 char visit[<<][][];

 int direct[][] = {{-,},{,},{,-},{,}};

 int n, m, time;

 int bfs(int bx, int by) {

     int x, y, key, t;

     int i, tmp;

     queue<node_st> que;

     node_st node;

     memset(visit, , sizeof(visit));

     visit[bx][by][] = ;

     que.push(node_st(bx,by,,));

     while ( !que.empty() ) {

         node = que.front();

         if (node.t >= time)

             return -;

         if (map[node.x][node.y] == '^')

             return node.t;

         que.pop();

         t = node.t + ;

         for (i=; i<; ++i) {

             x = node.x + direct[i][];

             y = node.y + direct[i][];

             if (x< || x>=n || y< || y>=m)

                 continue;

             if (map[x][y]>='a' && map[x][y]<='j')

                 key = node.key | (<<(map[x][y]-'a'));

             else

                 key = node.key;

             if (visit[key][x][y] || map[x][y]=='*')

                 continue;

             if (map[x][y]>='A' && map[x][y]<='J') {

                 tmp = (<<(map[x][y]-'A')) & key;

                 if ( !tmp )

                     continue;

             }

             que.push(node_st(x,y,t,key));

             visit[key][x][y] = ;

         }

     }

     return -;

 }

 int main() {

     int bx, by;

     int i, j;

     while (scanf("%d %d %d", &n, &m, &time) != EOF) {

         for (i=; i<n; ++i) {

             scanf("%s", map[i]);

             for (j=; j<m; ++j) {

                 if (map[i][j] == '@') {

                     bx = i;

                     by = j;

                 }

             }

         }

         i = bfs(bx, by);

         printf("%d\n", i);

     }

     return ;

 }