#include <iostream>
#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <vector>
#include <queue>
#define MAX_N 35
#define MAX_P 905
#define MAX_I 15
#define INF 0x3f3f3f3f
#define pii pair<int, int>
#define int long long

using namespace std;

int n, m, tot = 0, ans = INF;
int a[MAX_I];
int id[MAX_N][MAX_N];
int dis[MAX_I][MAX_P];
char s[MAX_N][MAX_N];
bool vis[MAX_P];
vector<int> e[MAX_P];
vector<pii> v;

void add(int a, int b, int c, int d) {
    int x = id[a][b], y = id[c][d];
    if (s[a][b] != '#' && s[c][d] != '#') {
        e[x].push_back(y);
        e[y].push_back(x);
    }
}

void dij(int s, int *dis) {
    priority_queue<pii, vector<pii>, greater<pii> > q;
    for (int i = 1; i <= tot; i++) {
        dis[i] = INF;
        vis[i] = false;
    }
    dis[s] = 0;
    q.push(pii(0, s));
    while (!q.empty()) {
        int x = q.top().second;
        q.pop();
        if (vis[x]) {
            continue;
        }
        vis[x] = true;
        for (int i = 0; i < e[x].size(); i++) {
            int t = e[x][i];
            if (dis[x] + 1 < dis[t]) {
                dis[t] = dis[x] + 1;
                q.push(pii(dis[t], t));
            }
        }
    }
}

signed main() {
    scanf("%lld%lld", &n, &m);
    for (int i = 1; i <= n; i++) {
        scanf("%s", s[i] + 1);
    }
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            if (s[i][j] != '#') {
                id[i][j] = ++tot;
            }
        }
    }
    for (int i = 1; i < n; i++) {
        for (int j = 1; j < m; j++) {
            add(i, j, i + 1, j);
            add(i, j, i, j + 1);
        }
    }
    for (int i = 1; i < n; i++) {
        add(i, m, i + 1, m);
    }
    for (int i = 1; i < m; i++) {
        add(n, i, n, i + 1);
    }
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            if (s[i][j] == '@') {
                v.push_back(pii(i, j));
            } else if (s[i][j] == 'p') {
                v.insert(v.begin(), pii(i, j));
            }
        }
    }
    for (int i = 0; i < v.size(); i++) {
        dij(id[v[i].first][v[i].second], dis[i]);
        a[i] = i;
    }
    int len = v.size();
    do {
        int s = dis[0][id[v[a[1]].first][v[a[1]].second]];
        for (int i = 2; i < len; i++) {
            s += dis[a[i - 1]][id[v[a[i]].first][v[a[i]].second]];
        }
        ans = min(ans, s);
    } while (next_permutation(a + 1, a + len));
    printf("%lld\n", ans < INF ? ans : -1);
}