1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <algorithm>
 5 #include <vector>
 6 #include <cmath>
 7 #include <queue>
 8 #include <stack>
 9 #include <map>
10 #include <string>
11 #include <set>
12 using namespace std;
13 typedef long long LL;
14 const double EPS = 1e-6;
15 const int INF = 2e9;
16 const LL LNF = 9e18;
17 const int MOD = 1e5;
18 const int MAXN = 1e3+10;
19
20 int row[110], sta[170], cnt[170], dp[110][170][170];
21 int main()
22 {
23     int n, m;
24     while(scanf("%d%d", &n,&m)!=EOF)
25     {
26         for(int i = 1; i<=n; i++)
27         {
28             int val;
29             row[i] = 0;
30             for(int j = 0; j<m; j++)
31             {
32                 scanf("%d", &val);
33                 row[i] += (val==0)*(1<<j);
34             }
35         }
36
37         int tot = 0;
38         for(int s = 0; s<(1<<m); s++)
39         {
40             if(!(s&(s<<2)))
41             {
42                 sta[++tot] = s;
43                 cnt[tot] = 0;
44                 for(int j = 0; j<m; j++)
45                     if(s&(1<<j))
46                         cnt[tot]++;
47             }
48         }
49
50         memset(dp, 0, sizeof(dp));
51         for(int i = 1; i<=n; i++)
52         {
53             for(int j = 1; j<=tot; j++)
54             {
55                 int s1 = sta[j];
56                 if(i>2 && (s1&row[i-2])) continue;
57                 for(int k = 1; k<=tot; k++)
58                 {
59                     int s2 = sta[k];
60                     if(i>1 && (s2&row[i-1])) continue;
61                     if(s1&(s2<<1) || (s1&(s2>>1)) ) continue;
62                     for(int t = 1; t<=tot; t++)
63                     {
64                         int s3 = sta[t];
65                         if(s3&row[i]) continue;
66                         if(s2&(s3<<1) || (s2&(s3>>1)) ) continue;
67                         if(s1&s3) continue;
68                         dp[i][k][t] = max(dp[i][k][t], dp[i-1][j][k]+cnt[t]);
69                     }
70                 }
71             }
72         }
73
74         int ans = 0;
75         for(int i = 1; i<=tot; i++)
76             for(int j = 1; j<=tot; j++)
77                 ans = max(ans, dp[n][i][j]);
78         printf("%d\n", ans);
79     }
80 }