1 //2017-08-12
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <iostream>
 5 #include <algorithm>
 6 #include <queue>
 7 
 8 using namespace std;
 9 
10 const int N = 210;
11 char G[N][N];
12 int n, m;
13 int dx[4] = {0, 1, 0, -1};
14 int dy[4] = {1, 0, -1, 0};
15 bool vis[N][N];
16 struct Node{
17     int x, y;
18     Node(int _x, int _y):x(_x), y(_y){}
19 };
20 
21 void bfs(int x, int y, int op){
22     Node node(x, y);
23     memset(vis, 0, sizeof(vis));
24     vis[x][y] = op+1;
25     G[x][y] = ‘#‘;
26     queue<Node> q;
27     q.push(node);
28     while(!q.empty()){
29         Node a = q.front();
30         q.pop();
31         for(int i = 0; i < 4; i++){
32             int nx = a.x + dx[i];
33             int ny = a.y + dy[i];
34             if(nx>=0 && nx < n && ny>=0 && ny < m && !vis[nx][ny] && G[nx][ny] == ‘0‘+op){
35                 Node tmp(nx, ny);
36                 q.push(tmp);
37                 vis[nx][ny] = op+1;
38                 G[nx][ny] = ‘#‘;
39             }
40         }
41     }
42 }
43 
44 int main()
45 {
46     //freopen("data1006.txt", "r", stdin);
47     while(scanf("%d%d", &n, &m)!=EOF){
48         for(int i = 0; i < n; i++){
49               scanf("%s", G[i]);
50         }
51         for(int i = 0; i < m; i++){
52             if(G[0][i] == ‘0‘)bfs(0, i, 0);
53             if(G[n-1][i] == ‘0‘)bfs(n-1, i, 0);
54         }
55         for(int i = 0; i < n; i++){
56             if(G[i][0] == ‘0‘)bfs(i, 0, 0);
57             if(G[i][m-1] == ‘0‘)bfs(i, m-1, 0);
58         }
59         int cnt1 = 0;
60         for(int i = 0; i < n; i++){
61             for(int j = 0; j < m; j++){
62                 if(G[i][j] == ‘1‘){
63                     bfs(i, j, 1);
64                     cnt1++;
65                 }
66             }
67         }
68         int cnt2 = 0;
69         for(int i = 0; i < n; i++){
70             for(int j = 0; j < m; j++){
71                 if(G[i][j] == ‘0‘){
72                     bfs(i, j, 0);
73                     cnt2++;
74                 }
75             }
76         }
77         if(cnt1==1 && cnt2 == 0)printf("1\n");
78         else if(cnt1 == 1 && cnt2 == 1)printf("0\n");
79         else printf("-1\n");
80     }
81 
82     return 0;
83 }