#include <bits/stdc++.h>

using namespace std;

#define DPRINTF(...) printf(__VA_ARGS_)
#define FOR0(i, n) for(int i=0;i<n;i++)
#define ALL(c) (begin(c)), (end(c))
#define fst(t) get<0>(t)
#define snd(t) get<1>(t)
#define thd(t) get<2>(t)

typedef long long ll;

int N, M; // H, W
vector<int> G[3000];
int match[3000];
bool used[3000];
std::string _map[50];
int dx[4] = {-1, 1, 0, 0}, dy[4] = {0, 0, -1, 1};

bool dfs(int v){
    used[v] = true;
    FOR0(i, G[v].size()){
        int u = G[v][i], w = match[u];
        if(w < 0 || !used[w] && dfs(w)){
            match[v] = u;
            match[u] = v;
            return true;
        }
    }
    return false;
}

int bipartite_matching(){
    int res = 0;
    memset(match, -1, sizeof(match));
    FOR0(v, N*M){
        if(match[v] < 0){
            memset(used, 0, sizeof(used));
            if(dfs(v)){
                res++;
            }
        }
    }
    return res;
}

int main(){
    cin >> N >> M;

    FOR0(i, N){
        cin >> _map[i];
    }

    int cnt[2];
    cnt[0] = cnt[1] = 0;
    FOR0(i, N){
        FOR0(j, M){
            if(_map[i][j] == '.'){continue;}
            cnt[(i+j)&1]++;

            FOR0(k, 4){
                int ny = i + dy[k], nx = j + dx[k];
                if(ny < 0 || ny >= N || nx < 0 || nx >= M){continue;}
                if(_map[ny][nx] == '.'){continue;}

                G[i*M+j].push_back(ny*M+nx);
                G[ny*M+nx].push_back(i*M+j);
            }
        }
    }

    int pair_n = bipartite_matching(),
        pair2_n = std::min(cnt[0], cnt[1]) - pair_n;
    printf("%d\n", pair_n * 100 + pair2_n * 10 + cnt[0] + cnt[1] - (pair_n + pair2_n) * 2);
}