#include <bits/stdc++.h>

using namespace std;

#define int long long
#define pb push_back
#define mp make_pair
#define pi pair<int,int>
#define f first
#define s second
#define lep(i,a,b) for (int i=(a); i <= (b); i++)
#define rep(i,b,a) for (int i = (b); i >= (a); i--)

char S[55][55]; int N, M;
map<pi, vector<pi>> adj;
map<int, vector<pi>> conn; map<pi, bool> vis;
int dx[] = {-1, 1, 0, 0};
int dy[] = {0, 0, -1, 1}; 

bool isValid(int i, int j) {
    return i >= 1 && j >= 1 && i <= N && j <= M && S[i][j] == '.';
}

void dfs(pi nn, int col) {
    vis[nn] = true;
    conn[col].push_back(nn);
    for (auto cc : adj[nn]) {
        if (!vis[cc]) 
            dfs(cc, col);
    }
}

signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cin >> N >> M;
    for (int i = 1; i <= N; ++i)
        for (int j = 1; j <= M; ++j) cin >> S[i][j];
    for (int i = 1; i <= N; ++i) {
        for (int j = 1; j <= M; ++j) {
            if (S[i][j] == '.') {
                for (int x = 0; x < 4; ++x) {
                        int xx = i + dx[x];
                        int yy = j + dy[x];
                        if (isValid(xx, yy)) {
                            adj[{i, j}].push_back({xx, yy});
                    }
                }
            }
        }
    }
    int k = 0;
    for (int i = 1; i <= N; ++i) {
        for (int j = 1; j <= M; ++j) {
            if (isValid(i, j) && !vis[{i, j}]) {
                dfs({i, j}, k);
                k++;
            }
        }
    }
    int ans = 0;
    for (auto pp : conn) {
        // cerr << pp.f << ":\n";
        int cnt0 = 0, cnt1 = 0;
        for (auto nn : pp.s) {
            // cerr << nn.f << " " << nn.s << endl;
            cnt0 += (nn.f + nn.s)&1;
            cnt1 += !((nn.f + nn.s)&1);
        }
        if (cnt0 == cnt1) continue;
        else ans += max(cnt0, cnt1);
    }
    cout << ans;
}