#include <iostream>
#include <algorithm>
#include <queue>
#include <cstring>
using namespace std;

bool visited[22][22][1 << 8];
int main()
{
    memset(visited, false, sizeof visited);
    int n, m;
    cin >> n >> m;

    char mat[n][m];
    int si, sj, ei, ej;
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < m; j++) {
            cin >> mat[i][j];
            if(mat[i][j] == 'P') {
                si = i;
                sj = j;
            }
            if(mat[i][j] == 'K') {
                ei = i;
                ej = j;
            }
        }
    }
    queue<int> Q;
    Q.push(si);
    Q.push(sj);
    Q.push(0); // ova ni e maska za da znaeme koi klucevi gi imame momentalno zemeno
    Q.push(0); // kolku cekori sme napravile do sega

    visited[si][sj][0] = true;

    int di[] = {-1, 1, 0, 0};
    int dj[] = {0, 0, -1, 1};
    while(!Q.empty()) {
        int ci = Q.front();
        Q.pop();
        int cj = Q.front();
        Q.pop();
        int keys = Q.front();
        Q.pop();
        int cekor = Q.front();
        Q.pop();

        if(ci == ei and cj == ej) {
            cout << cekor << endl;
            return 0;
        }
        for(int i = 0; i < 4; i++) {
            int ti = ci + di[i];
            int tj = cj + dj[i];
            if(ti >= 0 and ti < n and tj >= 0 and tj < m) {
                if(mat[ti][tj] == '#') {
                    continue;
                }
                if(mat[ti][tj] == '.' or mat[ti][tj] == 'K') {
                    if(!visited[ti][tj][keys]) {
                        Q.push(ti);
                        Q.push(tj);
                        Q.push(keys);
                        Q.push(cekor + 1);
                        visited[ti][tj][keys] = true;
                    }
                }
                if(mat[ti][tj] >= 'a' and mat[ti][tj] <= 'h') { // sme stapnale na kluc
                    int key_index = (mat[ti][tj] - 'a');
                    int new_keys = keys | (1 << key_index);
                    if(!visited[ti][tj][new_keys]) {
                        Q.push(ti);
                        Q.push(tj);
                        Q.push(new_keys);
                        Q.push(cekor + 1);
                        visited[ti][tj][new_keys] = true;
                    }
                }
                if(mat[ti][tj] >= 'A' and mat[ti][tj] <= 'H') {
                    int key_index = (mat[ti][tj] - 'A');
                    if(keys & (1 << key_index)) {
                        if(!visited[ti][tj][keys]) {
                            Q.push(ti);
                            Q.push(tj);
                            Q.push(keys);
                            Q.push(cekor + 1);
                            visited[ti][tj][keys] = true;
                        }
                    }
                }
            }
        }

    }
    cout << -1 << endl;
    return 0;
}
/*
 5 5
 P..#a
 A....
 .####
 K....
 #####

 10 10
 P.....d..f
 ####F#D###
 ..........
 ......h..b
 .#####H###
 .#....a...
 .#.###A###
 .#.#...c..
 .#.#.####C
 .B.#.#...K

3 3
P.A
##a
K..

 **/