#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <queue>
#include <iostream>
using namespace std;
const int N = 22;
int n,m,t;
int vis[N][N][1<<10]; ///第三维存的钥匙的状态
char graph[N][N];
struct Node{
    int x,y,step,state;
}s;
int dir[][2] = {{-1,0},{1,0},{0,1},{0,-1}};
bool check(int x,int y){
    if(x<1||y<1||x>n||y>m||graph[x][y]==‘*‘) return false;
    return true;
}
int bfs(){
    memset(vis,false,sizeof(vis));
    queue<Node> q;
    q.push(s);
    vis[s.x][s.y][0] = 0;
    while(!q.empty()){
        Node now = q.front();
        q.pop();
        if(now.step>=t) return -1;
        if(graph[now.x][now.y]==‘^‘) return now.step;
        Node next;
        for(int i=0;i<4;i++){
            next.x = now.x+dir[i][0];
            next.y = now.y+dir[i][1];
            next.step = now.step+1;
            next.state = now.state;
            if(!check(next.x,next.y)||vis[next.x][next.y][next.state]) continue;
            char c = graph[next.x][next.y];
            if(isupper(c)){
                int t = c-‘A‘;
                if(!((1<<t)&next.state)) continue;
            }
            if(islower(c)){
                int t = c-‘a‘;
                next.state = (1<<t)|next.state;
            }
            if(!vis[next.x][next.y][next.state]){
                vis[next.x][next.y][next.state] = true;
                q.push(next);
            }
        }
    }
    return -1;  ///没加这句wa无数发....因为它有可能在前面两个出口都没出去..以后写程序一定要严谨点
}
int main(){
    while(scanf("%d%d%d",&n,&m,&t)!=EOF){
        for(int i=1;i<=n;i++){
            scanf("%s",graph[i]+1);
            for(int j=1;j<=m;j++){
                if(graph[i][j]==‘@‘){
                    graph[i][j]=‘.‘;
                    s.x = i;
                    s.y = j;
                    s.step = 0;
                    s.state = 0;
                }
            }
        }
        printf("%d\n",bfs());
    }
}