#include<bits/stdc++.h>
using namespace std;
#define ALL(x) x.begin(),x.end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define mod 1000000007
using ll=long long;
const int INF=1000000000;
const ll LINF=1001002003004005006ll;
int dx[]={1,0,-1,0},dy[]={0,1,0,-1};
// ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return true;}return false;}

struct IOSetup{
    IOSetup(){
        cin.tie(0);
        ios::sync_with_stdio(0);
        cout<<fixed<<setprecision(12);
    }
} iosetup;
 
template<typename T1,typename T2>
ostream &operator<<(ostream &os,const pair<T1,T2>&p){
    os<<p.first<<" "<<p.second;
    return os;
}
 
template<typename T>
ostream &operator<<(ostream &os,const vector<T>&v){
    for(int i=0;i<(int)v.size();i++) os<<v[i]<<(i+1==(int)v.size()?"":" ");
    return os;
}

template<typename T1,typename T2>
istream &operator>>(istream &is,pair<T1,T2>&p){
    is>>p.first>>p.second;
    return is;
}

template<typename T>
istream &operator>>(istream &is,vector<T>&v){
    for(T &x:v)is>>x;
    return is;
}

template<typename flow_t, typename cost_t>
struct PrimalDual{
    const cost_t TINF;
 
    struct edge{
        int to;
        flow_t cap;
        cost_t cost;
        int rev;//この辺の逆辺がg[from]の何番目にあるか
        bool isrev;
    };
 
    vector<vector<edge>> graph;
    vector<cost_t> potential,min_cost;
    vector<int> prevv,preve;//点，辺
 
    PrimalDual(int V):graph(V),TINF(numeric_limits<cost_t>::max()){}
 
    void add_edge(int from,int to,flow_t cap,cost_t cost){
        graph[from].push_back((edge){to,cap,cost,(int)graph[to].size(),false});
        graph[to].push_back((edge){from,0,-cost,(int)graph[from].size()-1,true});
    }
 
    cost_t min_cost_flow(int s,int t,flow_t f){
        int V=(int)graph.size();
        cost_t ret=0;
        using Pi=pair<cost_t,int>;
        priority_queue<Pi,vector<Pi>,greater<Pi>> que;
        potential.assign(V,0);
        preve.assign(V,-1);
        prevv.assign(V,-1);
 
        while(f>0){
            min_cost.assign(V,TINF);
            que.emplace(0,s);
            min_cost[s]=0;
            //dijkstraパート
            while(!que.empty()){
                Pi p=que.top();que.pop();
                if(min_cost[p.second]<p.first) continue;
                for(int i=0;i<graph[p.second].size();i++){
                    edge &e=graph[p.second][i];
                    cost_t nextCost=min_cost[p.second]+e.cost+potential[p.second]-potential[e.to];
                    if(e.cap>0 and min_cost[e.to]>nextCost){
                        min_cost[e.to]=nextCost;
                        prevv[e.to]=p.second,preve[e.to]=i;
                        que.emplace(min_cost[e.to],e.to);
                    }
                }
            }
            if(min_cost[t]==TINF) return -1;
            //dijkstraの結果に応じてpotentialを上げ下げ
            for(int v=0;v<V;v++)potential[v]+=min_cost[v];
            flow_t addflow=f;
            for(int v=t;v!=s;v=prevv[v]){
                addflow=min(addflow,graph[prevv[v]][preve[v]].cap);
            }
            f-=addflow;
            ret+=addflow*potential[t];//天才じゃん
            for(int v=t;v!=s;v=prevv[v]){
                edge &e=graph[prevv[v]][preve[v]];
                e.cap-=addflow;
                graph[v][e.rev].cap+=addflow;
            }
        }
        return ret;
    }
 
    void output(){
        for(int i=0;i<graph.size();i++){
            for(auto &e:graph[i]){
                if(e.isrev)continue;
                auto &rev_e=graph[e.to][e.rev];
                cout<<i<<"->"<<e.to<<" (flow: "<<rev_e.cap<<" / "<<rev_e.cap+e.cap<<")"<<endl;
            }
        }
    }
};



signed main(){
    int h,w;cin>>h>>w;
    string s[h];
    rep(i,h) cin>>s[i];

    PrimalDual<ll,ll> flow(h*w+5);
    int src=h*w,sink=h*w+1;

    auto get=[&](int i,int j){
        return i*w+j;
    };

    int cnt=0;
    rep(i,h)rep(j,w){
        int u=get(i,j);
        if(s[i][j]!='#'){
            flow.add_edge(u,sink,1,0);
            if(i+1<h and s[i+1][j]!='#') flow.add_edge(u,get(i+1,j),flow.TINF,-1);
            if(j+1<w and s[i][j+1]!='#') flow.add_edge(u,get(i,j+1),flow.TINF,-1);
        }
        if(s[i][j]=='o'){
            flow.add_edge(src,u,1,0);
            cnt++;
        }
    }
    cout<<-flow.min_cost_flow(src,sink,cnt)<<endl;
    return 0;
}


Measured memory_bytes: 4256