#include <bits/stdc++.h>   using namespace std;   long long n, m, cnt, num, sub_d[(2600)], d[(2600)], root, cut[(2600)], t;   char s[55][55];   bool mark[(2600)], p, cycle;   vector<long long> e[(2600)];   void dfs(long long x, long long par = 0) {     bool tmp = 0;     if (!t) cnt++;     mark[x] = 1;     sub_d[x] = d[x];     for (int i = 0; i < e[x].size(); i++) {       if (mark[e[x][i]] && e[x][i] != par) cycle = 1;       if (!mark[e[x][i]]) {         d[e[x][i]] = d[x] + 1;         dfs(e[x][i], x);         sub_d[x] = min(sub_d[x], sub_d[e[x][i]]);         if (sub_d[e[x][i]] >= d[x]) tmp = 1;       } else if (e[x][i] != par)         sub_d[x] = min(sub_d[x], d[e[x][i]]);     }     cut[x] += tmp;   }   int main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     cin >> n >> m;     for (int i = 0; i < n; i++)       for (int j = 0; j < m; j++) {         cin >> s[i][j];         if (s[i][j] ==  # ) num++;       }     for (int i = 0; i < n; i++)       for (int j = 0; j < m; j++)         for (int p = -1; p <= 1; p++)           for (int q = -1; q <= 1; q++)             if ((!p ^ !q) && i + p >= 0 && j + q >= 0 && i + p < n && j + q < m &&                 s[i][j] ==  #  && s[i + p][j + q] ==  # )               e[i * m + j].push_back((i + p) * m + j + q);     for (int i = 0; i < n * m && t < 2; i++)       if (s[i / m][i % m] ==  # ) {         for (int j = 0; j < n * m; j++) mark[j] = d[j] = sub_d[j] = 0;         root = i;         dfs(i);         t++;       }     for (int i = 0; i < n * m; i++)       if (cut[i] == 2) p = 1;     if (p)       cout << 1;     else if (cnt != num)       cout << 0;     else if (cycle)       cout << 2;     else       cout << -1;     return 0;   }   