#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < n; i++)
#define rep2(i, x, n) for(int i = x; i <= n; i++)
#define rep3(i, x, n) for(int i = x; i >= n; i--)
#define elif else if
#define sp(x) fixed << setprecision(x)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
using ll = long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
const int MOD = 1000000007;
//const int MOD = 998244353;
const int inf = (1<<30)-1;
const ll INF = (1LL<<60)-1;
const double pi = acos(-1.0);
const double EPS = 1e-10;
template<typename T> bool chmax(T &x, const T &y) {return (x < y)? (x = y, true) : false;};
template<typename T> bool chmin(T &x, const T &y) {return (x > y)? (x = y, true) : false;};

template<typename T>
struct Min_Cost_Flow{
    struct edge{
        int to; T cap, cost; int rev;
        edge(int to, T cap, T cost, int rev) : to(to), cap(cap), cost(cost), rev(rev) {}
    };

    vector<vector<edge>> es;
    vector<T> d, h;
    vector<int> pre_v, pre_e;
    const T INF_T;
    const int n;

    Min_Cost_Flow(int n) : INF_T(numeric_limits<T>::max()), n(n){
        es.resize(n), d.resize(n), h.resize(n), pre_v.resize(n), pre_e.resize(n);
    }

    void add_edge(int from, int to, T cap, T cost){
        es[from].eb(to, cap, cost, sz(es[to]));
        es[to].eb(from, 0, -cost, sz(es[from])-1);
    }

    void bellman_ford(int s){
        fill(all(h), INF_T);
        h[s] = 0;
        while(true){
            bool update = false;
            rep(i, n){
                if(h[i] == INF_T) continue;
                for(auto &e: es[i]){
                    if(e.cap > 0 && chmin(h[e.to], h[i]+e.cost)){
                        update = true;
                    }
                }
            }
            if(!update) break;
        }
    }

    void dijkstra(int s){
        fill(all(d), INF_T);
        using P = pair<T, int>;
        priority_queue<P, vector<P>, greater<P> > que;
        que.emplace(d[s] = 0, s);
        while(!que.empty()){
            T p; int i;
            tie(p, i) = que.top(); que.pop();
            if(p > d[i]) continue;
            rep(j, sz(es[i])){
                edge &e = es[i][j];
                if(e.cap > 0 && chmin(d[e.to], d[i]+e.cost+h[i]-h[e.to])){
                    pre_v[e.to] = i, pre_e[e.to] = j;
                    que.emplace(d[e.to], e.to);
                }
            }
        }
    }

    T min_cost_flow(int s, int t, T flow){
        T ret = 0;
        bellman_ford(s);
        while(flow > 0){
            dijkstra(s);
            if(d[t] == INF_T) return -1;
            rep(i, sz(es)){
                if(h[i] == INF_T || d[i] == INF_T) h[i] = INF_T;
                else h[i] += d[i];
            }
            T f = flow;
            for(int now = t; now != s; now = pre_v[now]){
                chmin(f, es[pre_v[now]][pre_e[now]].cap);
            }
            ret += f*h[t], flow -= f;
            for(int now = t; now != s; now = pre_v[now]){
                edge &e = es[pre_v[now]][pre_e[now]];
                e.cap -= f, es[now][e.rev].cap += f;
            }
        }
        return ret;
    }
};

int main(){
    int H, W;
    cin >> H >> W;
    string S[H];
    rep(i, H) cin >> S[i];
    int N = H*W;
    Min_Cost_Flow<ll> G(N+2);
    int s = N, t = N+1;
    int dx[] = {1, 0}, dy[] = {0, 1};
    int f = 0;
    rep(i, H){
        rep(j, W){
            if(S[i][j] == '#') continue;
            G.add_edge(W*i+j, t, 1, 0);
            rep(k, 2){
                int ni = i+dx[k], nj = j+dy[k];
                if(ni >= H || nj >= W || S[ni][nj] == '#') continue;
                G.add_edge(W*i+j, W*ni+nj, INF, -1);
            }
            if(S[i][j] != 'o') continue;
            G.add_edge(s, W*i+j, 1, 0);
            f++;
        }
    }
    cout << -G.min_cost_flow(s, t, f) << endl;
}

Measured memory_bytes: 4368