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//Solução do problema para apenas um caso de teste
#include<bits/stdc++.h>
#define MAXN 510
#define pii pair<int,int>

using namespace std;

char m[MAXN][MAXN];
int marc[MAXN][MAXN];
int dist[MAXN][MAXN];

int l, c;

int dx[] = {0, 0, 1, -1};
int dy[] = {1, -1, 0, 0};

vector<pii> focos;

void bfs_ms(){
    queue<pii> q;
    for(auto e : focos){
        q.push(e);
        marc[e.first][e.second] = 1;
        dist[e.first][e.second] = 0;
    }
    while(!q.empty()){
        pii v = q.front(); q.pop();
        int x = v.first;
        int y = v.second;
        for(int k = 0; k <= 3; k++){
            int nx = x + dx[k];
            int ny = y + dy[k];
            if(nx < 0 || nx >= l) continue;
            if(ny < 0 || ny >= c) continue;
            if(m[nx][ny] == '#' || marc[nx][ny] == 1) continue;
            q.push({nx, ny});
            marc[nx][ny] = 1;
            dist[nx][ny] = dist[x][y]+1;
        }
    }
}


int bfs(pii s){
    memset(marc, 0, sizeof marc);
    queue<pii> q;
    q.push(s);
    marc[s.first][s.second] = 1;
    dist[s.first][s.second] = 0;

    while(!q.empty()){
        pii v = q.front(); q.pop();
        int x = v.first;
        int y = v.second;

        if(x == 0 || x == l-1 || y == 0 || y == c-1) return dist[x][y]+1;

        for(int k = 0; k <= 3; k++){
            int nx = x + dx[k];
            int ny = y + dy[k];
            if(nx < 0 || nx >= l) continue;
            if(ny < 0 || ny >= c) continue;
            if(m[nx][ny] == '#' || marc[nx][ny] == 1) continue;
            if(dist[x][y]+1 < dist[nx][ny]){
                q.push({nx, ny});
                marc[nx][ny] = 1;
                dist[nx][ny] = dist[x][y]+1;
            }
        }
    }

    return -1;
}

int main(){
    scanf("%d %d",&c, &l);

    pii ini;

    for(int i = 0; i < l; i++){
        for(int j = 0; j < c; j++){
            scanf(" %c", &m[i][j]);
            if(m[i][j] == '*') focos.push_back({i,j});
            if(m[i][j] == '@') ini = {i,j};
        }
    }

    bfs_ms();

    //for(int i = 0; i < l; i++){
    //    for(int j = 0; j < c; j++){
    //        printf("%d ", marc[i][j]);
    //    }
    //    printf("\n");
    //}

    int resp = bfs(ini);

    printf("%d", resp);
}