//By SiriusRen#include <queue>#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int N=222,M=N*N*21;int n,m,a[N][N],color[N][N],id[N][N],S=0,jy,ans,sum;int first[M],next[M],v[M],w[M],vis[M/16],tot,T,cnt;char xx[]={1,-1,2,-2,1,-1,2,-2};char yy[]={2,-2,1,-1,-2,2,-1,1};void Add(int x,int y,int z){w[tot]=z,v[tot]=y,next[tot]=first[x],first[x]=tot++;}void add(int x,int y,int z){Add(x,y,z),Add(y,x,0);}bool tell(){    memset(vis,-1,sizeof(vis));vis[S]=0;    queue<int>q;q.push(S);    while(!q.empty()){        int t=q.front();q.pop();        for(int i=first[t];~i;i=next[i])            if(w[i]&&vis[v[i]]==-1)                q.push(v[i]),vis[v[i]]=vis[t]+1;    }    return vis[T]!=-1;}int zeng(int x,int y){    if(x==T)return y;    int r=0;    for(int i=first[x];y>r&&~i;i=next[i])        if(w[i]&&vis[v[i]]==vis[x]+1){            int t=zeng(v[i],min(y-r,w[i]));            w[i]-=t,w[i^1]+=t,r+=t;        }    if(!r)vis[x]=-1;    return r;}bool check(int x,int y){    if(x<1||x>n||y<1||y>m||a[x][y])return false;    return true;}int main(){    memset(first,-1,sizeof(first));    scanf("%d%d",&n,&m);T=n*m+1;    for(int i=1;i<=n;i++)        for(int j=1;j<=m;j++){            id[i][j]=++cnt;            scanf("%d",&a[i][j]);            if((i+j)&1){color[i][j]=1,add(S,id[i][j],1);}            else add(id[i][j],T,1);            if(!a[i][j])sum++;        }    for(int i=1;i<=n;i++)        for(int j=1;j<=m;j++)            if(color[i][j]&&!a[i][j])                for(int k=0;k<8;k++){                    int tx=i+xx[k],ty=j+yy[k];                    if(check(tx,ty))add(id[i][j],id[tx][ty],1);                }    while(tell())while(jy=zeng(S,0x3f3f3f3f))ans+=jy;    printf("%d\n",sum-ans);}