#include <iostream>

#include <cstdio>

#include <cmath>

#include <vector>

#include <cstring>

#include <string>

#include <algorithm>

#include <string>

#include <set>

#include <functional>

#include <numeric>

#include <sstream>

#include <stack>

#include <map>

#include <queue>

#pragma comment(linker, "/STACK:102400000,102400000")

#define CL(arr, val)    memset(arr, val, sizeof(arr))

#define ll long long

#define inf 0x7f7f7f7f

#define lc l,m,rt<<1

#define rc m + 1,r,rt<<1|1

#define pi acos(-1.0)

#define L(x)    (x) << 1

#define R(x)    (x) << 1 | 1

#define MID(l, r)   (l + r) >> 1

#define Min(x, y)   (x) < (y) ? (x) : (y)

#define Max(x, y)   (x) < (y) ? (y) : (x)

#define E(x)        (1 << (x))

#define iabs(x)     (x) < 0 ? -(x) : (x)

#define OUT(x)  printf("%I64d\n", x)

#define lowbit(x)   (x)&(-x)

#define Read()  freopen("a.txt", "r", stdin)

#define Write() freopen("b.txt", "w", stdout);

#define maxn 1000000000

#define N 2510

#define mod 1000000000

using namespace std;

struct point

{

    int x,y,step,state;

};

int n,m,t;

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

char maze[][];

int vis[][][<<];

int ex,ey;

int get(char c)

{

    return c-(islower(c)?'a':'A');  //转化为 数字 'a'为0

}

void bfs(int sx,int sy)

{

    point s;

    s.x=sx,s.y=sy,s.step=,s.state=;

    memset(vis,,sizeof(vis));

    vis[s.x][s.y][]=;

    queue<point>que;

    que.push(s);

    while(!que.empty())

    {

        point e=que.front(); que.pop();

      //  printf("%d %d %d %d\n",e.x,e.y,e.step,e.state);

        if(e.x==ex&&e.y==ey) {printf("%d\n",e.step);return;}

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

        {

            s.x=e.x+dir[i][];

            s.y=e.y+dir[i][];

            s.state=e.state;

            if(s.x>=&&s.x<n&&s.y>=&&s.y<m&&maze[s.x][s.y]!='*')

            {

                //判断是否有相应钥匙

                if(isupper(maze[s.x][s.y])&&(!(e.state&(<<get(maze[s.x][s.y]))))) continue;

                if(islower(maze[s.x][s.y])) //遇到钥匙

                {

                    //printf("%d\n",1<<get(maze[s.x][s.y]));

                    s.state|=(<<get(maze[s.x][s.y]));

                }

                s.step=e.step+;

                if(!vis[s.x][s.y][s.state]&&s.step<=t)

                {

                    vis[s.x][s.y][s.state]=;

                    que.push(s);

                }

            }

        }

    }

    printf("-1\n");

}

int main()

{

    //freopen("a.txt","r",stdin);

    int sx,sy;

    while(~scanf("%d%d%d",&n,&m,&t))

    {

        t--;

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

        {

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

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

                if(maze[i][j]=='@')

                {

                    sx=i,sy=j;

                }

                else if(maze[i][j]=='^')

                {

                    ex=i,ey=j;

                }

        }

       // printf("%d %d\n",sx,sy);

        bfs(sx,sy);

    }

    return ;

}