#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <queue>
#include <set>
using namespace std;
typedef long long ll;
#define rep(i, n) for(int i = 0; i < (n); i++)

template<class T>
using vi = vector<T>;

template<class T>
using vii = vector<vi<T>>;

template<class T>
using viii = vector<vii<T>>;



struct Dinic {
    struct edge {
        int to, rev; ll cap;
        edge(int t = 0, int r = 0, ll c = 0) : to(t), rev(r), cap(c) {}
    };

    int n;
    vii<edge> to;
    vi<int> iter;
    vi<int> dist;

    Dinic(int n_ = 0) : n(n_), to(n_), iter(n_), dist(n_) {}

    void addedge(int u, int v, ll cap) {
        int su = (int)to[u].size();
        int sv = (int)to[v].size();
        to[u].push_back({ v, sv, cap });
        to[v].push_back({ u, su, 0 });
    }

    void bfs(int s) {
        dist.assign(n, -1);
        dist[s] = 0;
        queue<int> q;
        q.push(s);

        while (!q.empty()) {
            int v = q.front();
            q.pop();
            for (edge& nv : to[v]) {
                if (dist[nv.to] >= 0 || nv.cap == 0) continue;
                dist[nv.to] = dist[v] + 1;
                q.push(nv.to);
            }
        }
    }

    ll dfs(int v, int t, ll f = 1e18) {
        if (v == t) return f;
        int sv = (int)to[v].size();
        for (int& i = iter[v]; i < sv; i++) {
            edge& nv = to[v][i];
            if (dist[nv.to] <= dist[v] || nv.cap == 0) continue;
            ll nf = dfs(nv.to, t, min(f, nv.cap));
            if (nf > 0) {
                nv.cap -= nf;
                to[nv.to][nv.rev].cap += nf;
                return nf;
            }
        }
        return 0;
    }

    ll maxflow(int s, int t) {
        ll res = 0, flow = 0;
        while (true) {
            bfs(s);
            if (dist[t] < 0) break;
            iter.assign(n, 0);
            while (flow = dfs(s, t)) res += flow;
        }
        return res;
    }
};

int main()
{
    int n, m;
    cin >> n >> m;
    vi<string> s(n);
    rep(i, n) cin >> s[i];

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

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

    Dinic dn(n * m + 2);
    int S = n * m, T = S + 1;
    int cw = 0, cb = 0;
    rep(i, n) rep(j, m) {
        if (s[i][j] == '.') continue;
        if ((i + j) & 1) {
            dn.addedge(f(i, j), T, 1);
            cb++;
        }
        else {
            dn.addedge(S, f(i, j), 1);
            cw++;
            rep(k, 4) {
                int ni = i + dx[k];
                int nj = j + dy[k];
                if (ni < 0 || ni >= n || nj < 0 || nj >= m || s[ni][nj] == '.') continue;
                dn.addedge(f(i, j), f(ni, nj), 1);
            }
        }
    }

    ll mf = dn.maxflow(S, T);
    cw -= mf, cb -= mf;
    ll res = mf * 100 + min(cw, cb) * 10 + cw + cb - 2 * min(cw, cb);
    cout << res << endl;

    return 0;
}