#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
//typedef __int128_t LL;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define F first
#define S second
#define pb push_back
mt19937 rnd;

#define cost_t ll
#define flow_t ll

struct mcSFlow{
    struct Edge{
        cost_t c;
        flow_t f;
        int to, rev;
        Edge(int _to, cost_t _c, flow_t _f, int _rev):c(_c), f(_f), to(_to), rev(_rev){}
    };
    static constexpr cost_t INFCOST = numeric_limits<cost_t>::max()/2;
    cost_t eps;
    int N, S, T;
    vector<vector<Edge> > G;
    vector<unsigned int> isq, cur;
    vector<flow_t> ex;
    vector<cost_t> h;
    mcSFlow(int _N, int _S, int _T):eps(0), N(_N), S(_S), T(_T), G(_N){}
    void add_edge(int a, int b, flow_t cap, cost_t cost){
		assert(cap>=0);
        assert(a>=0&&a<N&&b>=0&&b<N);
        if(a==b){assert(cost>=0); return;}
        cost*=N;
        eps = max(eps, abs(cost));
        G[a].emplace_back(b, cost, cap, G[b].size());
        G[b].emplace_back(a, -cost, 0, G[a].size()-1);
    }
    void add_flow(Edge& e, flow_t f) {
        Edge &back = G[e.to][e.rev];
        if (!ex[e.to] && f)
            hs[h[e.to]].push_back(e.to);
        e.f -= f; ex[e.to] += f;
        back.f += f; ex[back.to] -= f;
    }
    vector<vector<int> > hs;
    vector<int> co;
    flow_t max_flow() {
        ex.assign(N, 0);
        h.assign(N, 0); hs.resize(2*N);
        co.assign(2*N, 0); cur.assign(N, 0);
        h[S] = N;
        ex[T] = 1;
        co[0] = N-1;
        for(auto &e:G[S]) add_flow(e, e.f);
        if(hs[0].size())
        for (int hi = 0;hi>=0;) {
            int u = hs[hi].back();
            hs[hi].pop_back();
            while (ex[u] > 0) { // discharge u
                if (cur[u] == G[u].size()) {
                    h[u] = 1e9;
                    for(unsigned int i=0;i<G[u].size();++i){
                        auto &e = G[u][i];
                        if (e.f && h[u] > h[e.to]+1){
                            h[u] = h[e.to]+1, cur[u] = i;
                        }
                    }
                    if (++co[h[u]], !--co[hi] && hi < N)
                        for(int i=0;i<N;++i)
                            if (hi < h[i] && h[i] < N){
                                --co[h[i]];
                                h[i] = N + 1;
                            }
                    hi = h[u];
                } else if (G[u][cur[u]].f && h[u] == h[G[u][cur[u]].to]+1)
                    add_flow(G[u][cur[u]], min(ex[u], G[u][cur[u]].f));
                else ++cur[u];
			}
            while (hi>=0 && hs[hi].empty()) --hi;
        }
        return -ex[S];
    }
    void push(Edge &e, flow_t amt){
        if(e.f < amt) amt=e.f;
        e.f-=amt; ex[e.to]+=amt;
        G[e.to][e.rev].f+=amt; ex[G[e.to][e.rev].to]-=amt;
    }
    void relabel(int vertex){
        cost_t newHeight = -INFCOST;
        for(unsigned int i=0;i<G[vertex].size();++i){
            Edge const&e = G[vertex][i];
            if(e.f && newHeight < h[e.to]-e.c){
                newHeight = h[e.to] - e.c;
                cur[vertex] = i;
            }
        }
        h[vertex] = newHeight - eps;
    }
    static constexpr int scale=2;
    pair<flow_t, cost_t> minCostMaxFlow(){
        cost_t retCost = 0;
        for(int i=0;i<N;++i)
            for(Edge &e:G[i])
                retCost += e.c*(e.f);
        //find max-flow
        flow_t retFlow = max_flow();
        h.assign(N, 0); ex.assign(N, 0);
        isq.assign(N, 0); cur.assign(N,0);
        queue<int> q;
        for(;eps;eps>>=scale){
            //refine
            fill(cur.begin(), cur.end(), 0);
            for(int i=0;i<N;++i)
                for(auto &e:G[i])
                    if(h[i] + e.c - h[e.to] < 0 && e.f) push(e, e.f);
            for(int i=0;i<N;++i){
                if(ex[i]>0){
                    q.push(i);
                    isq[i]=1;
                }
            }
            // make flow feasible
            while(!q.empty()){
                int u=q.front();q.pop();
                isq[u]=0;
                while(ex[u]>0){
                    if(cur[u] == G[u].size())
                        relabel(u);
                    for(unsigned int &i=cur[u], max_i = G[u].size();i<max_i;++i){
                        Edge &e=G[u][i];
                        if(h[u] + e.c - h[e.to] < 0){
                            push(e, ex[u]);
                            if(ex[e.to]>0 && isq[e.to]==0){
                                q.push(e.to);
                                isq[e.to]=1;
                            }
                            if(ex[u]==0) break;
                        }
                    }
                }
            }
            if(eps>1 && eps>>scale==0){
                eps = 1<<scale;
            }
        }
        for(int i=0;i<N;++i){
            for(Edge &e:G[i]){
                retCost -= e.c*(e.f);
            }
        }
        return make_pair(retFlow, retCost/2/N);
    }
    flow_t getFlow(Edge const &e){
        return G[e.to][e.rev].f;
    }
};

const int M = 50 + 5;
char a[M][M];
bool dp[M][M];

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
#ifdef LOCAL
    freopen("input.txt", "r", stdin);
#endif

    int n, m;
    cin >> n >> m;
    for (int i = 0; i <= n + 1; i++) {
        for (int j = 0; j <= m + 1; j++) {
            a[i][j] = '#';
        }
    }
    vector<pii> pos;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            cin >> a[i][j];
            if (a[i][j] == 'o') {
                pos.pb({i, j});
            }
        }
    }
    int k = pos.size();
    int src = 0, tar = k + n * m + 1;
    mcSFlow f(n * m + k + 2, src, tar);
    for (int i = 1; i <= k; i++) {
        f.add_edge(src, i, 1, 0);
    }
    for (int i = k + 1; i <= k + n * m; i++) {
        f.add_edge(i, tar, 1, 0);
    }
    for (int l = 0; l < k; l++) {
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= m; j++) {
                dp[i][j] = 0;
            }
        }
        dp[pos[l].F][pos[l].S] = 1;
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= m; j++) {
                if (a[i][j] != '#') {
                    dp[i][j] |= dp[i - 1][j] | dp[i][j - 1];
                    if (dp[i][j]) {
                        f.add_edge(l + 1, k + (i - 1) * m + j, 1, - (i - pos[l].F) - (j - pos[l].S));
                    }
                }
            }
        }
    }
    pair<ll, ll> ans = f.minCostMaxFlow();
    cout << -ans.S << "\n";

#ifdef LOCAL
    cerr << "\nTime elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
#endif
    return 0;
}


Measured memory_bytes: 8108