#include "cstdio"

#include "cstring"

#include "string"

#include "iostream"

#include "queue"

using namespace std;

int n,m,t,sx,sy,ex,ey,f[][][],dir[][]={-,,,,,-,,},ans;

char map[][];

struct status

{

    int x,y,dep,key;

    status(int x,int y,int dep,int key):x(x),y(y),dep(dep),key(key) {}

};

void bfs(int x,int y)

{

    queue<status> Q;

    Q.push(status(x,y,,));

    f[x][y][]=;

    bool flag=false;

    while(!Q.empty())

    {

        if(flag) break;

        status t=Q.front();Q.pop();

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

        {

            int X=t.x+dir[s][],Y=t.y+dir[s][],key=t.key;

            if(X<||X>n||Y<||Y>m||map[X][Y]=='*') continue;

            if(isupper(map[X][Y]))

            {

                int k=map[X][Y]-'A';

                if(!(key&(<<k))) continue;

            }

            if(islower(map[X][Y]))

            {

                int k=map[X][Y]-'a';

                key=t.key|(<<k);

            }

            if(f[X][Y][key]) continue;

            f[X][Y][key]=;

            if(X==ex&&Y==ey) {flag=true;ans=min(ans,t.dep+);}

            Q.push(status(X,Y,t.dep+,key));

        }

    }

}

int main()

{

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

    ios::sync_with_stdio(false);

    string tt;

    while(cin>>n>>m>>t)

    {

        memset(f,,sizeof(f));

        ans=<<;

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

        {

           cin>>tt;

           for(int j=;j<tt.size();j++)

           {

               map[i][j+]=tt[j];

               if(tt[j]=='@') {sx=i;sy=j+;}

               if(tt[j]=='^') {ex=i;ey=j+;}

           }

        }

        bfs(sx,sy);

        if(ans<t) cout<<ans<<endl;

        else cout<<"-1"<<endl;

    }

}