#include<bits/stdc++.h>
#define ff first
#define ss second
#define pb push_back
typedef long long ll;
using namespace std;
typedef pair<int,int> pii;

const int mod=998244353;
inline int add(int x,int y){int ret=x+y;if(ret>=mod)ret-=mod;return ret;}
inline int sub(int x,int y){int ret=x-y;if(ret<0)ret+=mod;return ret;}
inline int mul(int x,int y){return ((ll)x*y)%mod;}
inline int step(int base,int pw){int ret=1;while(pw){if(pw&1)ret=mul(ret,base);base=mul(base,base);pw>>=1;}return ret;}
inline int invv(int x){return step(x,mod-2);}


const int maxn=4010;
int a[maxn/2][maxn/2];
ll nc2(ll x){
    return ((x-1)*x)/2;
}


struct edge{
    int a,b,f;
};
vector<edge>e;
vector<int>g[maxn];
int level[maxn],sink,source,cnt,start[maxn];
void add_edge(int a,int b){
    g[a].pb(e.size());
    e.pb({a,b,0});
    g[b].pb(e.size());
    e.pb({b,a,1});

    ///printf("%d %d AAA\n",a,b);
}
int bfs(){
    queue<int>q;
    q.push(source);
    memset(level,0,sizeof(level));
    level[source]=1;
    while(q.size()){
        int x=q.front();
        q.pop();
        for(int i=0;i<g[x].size();i++){
            int id=g[x][i];
            if(e[id].f || level[e[id].b])continue;
            level[e[id].b]=level[x]+1;
            q.push(e[id].b);
        }
    }
    return level[sink];
}
int sflow(int x){
    if(x==sink)return 1;
    for(;start[x]<g[x].size();start[x]++){
        int id=g[x][start[x]];
        if(e[id].f==0 && level[x]+1==level[e[id].b]){
            int tmp=sflow(e[id].b);
            if(tmp){
                e[id].f^=1;
                e[id^1].f^=1;
                return 1;
            }
        }
    }
    return 0;
}
vector<int>lside;
vector<int>vect[maxn];
int lpos[maxn],match[maxn];
ll full=0;

int nid[maxn/2][maxn/2];
int n,m;
map<int,pii>mapa;
int get_id(int x,int y){
    if(nid[x][y]==0){
        nid[x][y]=++cnt;
        ///mapa[cnt]={x,y};
    }
    return nid[x][y];
}
pii get_pos(int id){
    return mapa[id];
}

void goflow(){

    while(bfs()){
        memset(start,0,sizeof(start));
        int ret;
        while(ret=sflow(source)){full--;}
    }

    for(int i=0;i<g[source].size();i++){
        int id=g[source][i];
        lside.pb(e[id].b);
        lpos[e[id].b]=1;
    }

    for(int i=source+1;i<sink;i++){

        for(int j=0;j<g[i].size();j++){
            int id=g[i][j];
            if(e[id].b==source || e[id].b==sink)continue;

            if(e[id].f){
                if(lpos[i]){
                    match[i]=e[id].b;
                    //printf("%d %d | %d %d | %d %d \n",get_pos(i).ff,get_pos(i).ss,get_pos(e[id].b).ff,get_pos(e[id].b).ss,i,e[id].b);
                    //printf("%d %d %d AA\n",e[id].a,e[id].b,e[id].f);
                }
                continue;
            }
            vect[i].pb(e[id].b);
        }

    }

}
void make_graph(){

    int dx[4]={0,0,1,-1};
    int dy[4]={1,-1,0,0};

    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){

            if((i+j)%2 || a[i][j]==0)continue;

            for(int k=0;k<4;k++){
                int idx=i+dx[k];
                int idy=j+dy[k];
                if(idx<1 || idy<1 || idx>n || idy>m || a[idx][idy]==0)continue;

                add_edge(get_id(i,j),get_id(idx,idy));
            }

        }
    }

    source=0;
    sink=++cnt;

    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){

            if(a[i][j]==0)continue;

            if((i+j)%2)add_edge(get_id(i,j),sink);
            else add_edge(source,get_id(i,j));

        }
    }

}

int pos[maxn];
void dfs(int x){
    pos[x]=1;
    for(int i=0;i<vect[x].size();i++){
        int id=vect[x][i];
        if(pos[id])continue;
        dfs(id);
    }
}
void sub_good(){

    for(int i=0;i<lside.size();i++){
        int id=lside[i];

        memset(pos,0,sizeof(pos));
        dfs(id);

        for(int j=source+1;j<sink;j++){
            if(lpos[j])continue;
            if(j==match[id])continue;
            if(pos[j])full--;
        }

    }

}

int main(){

    ///freopen("test.txt","r",stdin);

    scanf("%d %d",&n,&m);
    int ncnt[2]={0,0};
    for(int i=1;i<=n;i++){
        string s;
        cin>>s;
        for(int j=1;j<=m;j++){
            if(s[j-1]=='.'){
                a[i][j]=1;
                ncnt[(i+j)%2]++;
            }
            else a[i][j]=0;
        }
    }

    if(nc2(ncnt[0])+nc2(ncnt[1])>=1000000){
        printf("1000000\n");
        return 0;
    }

    full=nc2(ncnt[0]+ncnt[1]);
    make_graph();
    goflow();

    sub_good();

    printf("%lld\n",full);

    return 0;
}