/*
记录状态的bfs，用到了二进制状态压缩
http://acm.hdu.edu.cn/showproblem.php?pid=1429
*/
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include<queue>
#define N 20010
using namespace std;
struct State
{
int x,y,key,step;
State(int x1,int y1,int key1,int step1)
{
x=x1,y=y1,key=key1,step=step1;
}
};
int n,m,les,sx,sy,vis[21][21][1025];
char map[21][21];
int dx[]={0,0,1,-1};
int dy[]={1,-1,0,0};
inline bool check(State T)
{
if(T.x>0&&T.y>0&&T.x<=n&&T.y<=m&&map[T.x][T.y]!='*'&&T.step<les)
return true;
return false;
}
int bfs()
{
queue<State> q;
memset(vis,0,sizeof(vis));
q.push(State(sx,sy,0,0));
vis[sx][sy][0]=1;
while(q.size())
{
State src=q.front();q.pop();
for(int j=0;j<4;j++)
{
State cur=State(src.x+dx[j],cur.y=src.y+dy[j],cur.key=src.key,cur.step=src.step+1);
if(check(cur)&&!vis[cur.x][cur.y][cur.key])
{
vis[cur.x][cur.y][cur.key]=1;
if(map[cur.x][cur.y]=='^')return cur.step;
else if(map[cur.x][cur.y]=='.')
q.push(cur);
else if(map[cur.x][cur.y]>='a'&&map[cur.x][cur.y]<='j')
{
cur.key=cur.key|(1<<(map[cur.x][cur.y]-'a'));
q.push(cur);
}
else if(map[cur.x][cur.y]>='A'&&map[cur.x][cur.y]<='J'&&(cur.key&(1<<(map[cur.x][cur.y]-'A'))))
{
q.push(cur);
}
}
}
}
return -1;
}
int main()
{
while(scanf("%d%d%d",&n,&m,&les)!=EOF)
{
getchar();
for(int i=1;i<=n;i++)
{
for(int j=1;j<=m;j++)
{
map[i][j]=getchar();
if(map[i][j]=='@')
{
sx=i,sy=j;
map[i][j]='.';
}
}
getchar();
}
cout<<bfs()<<endl;
getchar();
}
}
