#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <queue>
#include <set>
using namespace std;

struct Dinic {
	static const int INF = 1e9;

	struct E {
		//to,容量,逆辺のindex
		int to, cap, rev;
		E(int t, int c, int r) {
			to = t;
			cap = c;
			rev = r;
		}
	};

	//最大頂点数
	int MAX_V;
	vector<vector<E>>G;
	Dinic(int max_v) {
		MAX_V = max_v;
		G.resize(MAX_V);
	}

	//有向辺
	inline void add_edge(int from, int to, int cap) {
		if (from == to)return;
		G[from].push_back(E(to, cap, G[to].size()));
		G[to].push_back(E(from, 0, G[from].size()-1));
	}

	//無向辺
	inline void add_undirected_edge(int from, int to, int cap) {
		if (from == to)return;
		G[from].push_back(E(to, cap, G[to].size()));
		G[to].push_back(E(from, cap, G[from].size()-1));
	}

	//深さ
	vector<int>level;

	//深さのラベル付け
	void bfs(int s) {
		level.assign(MAX_V, -1);
		queue<int> que;
		level[s] = 0;
		que.push(s);
		while (!que.empty()) {
			int v = que.front(); que.pop();
			for (int i = 0; i < G[v].size(); i++) {
				E &e = G[v][i];
				if (e.cap > 0 && level[e.to] < 0) {
					level[e.to] = level[v] + 1;
					que.push(e.to);
				}
			}
		}
	}

	//s -- v -- u -- t
	//tから深さ優先探索
	int dfs(int s, int u, int crr) {
		if (s == u || crr == 0)return crr;

		int sum = 0;

		for (int i = 0; i < G[u].size(); i++) {
			E& e = G[u][i];				//t側
			E& ee = G[e.to][e.rev];		//s側

			int v = e.to;
			if (level[v] >= level[u] || ee.cap <= 0)continue;

			int f = dfs(s, v, min(crr - sum, ee.cap));
			if (f <= 0)continue;

			//容量の更新
			ee.cap -= f;
			e.cap += f;

			//流量の更新
			sum += f;

			if (sum == crr)break;
		}

		return sum;
	}

	int max_flow(int s, int t) {
		int flow = 0;
		//tに流せなくなるまで
		while(1){
			bfs(s);
			if (level[t] < 0)return flow;
			flow += dfs(s, t, INF);
		}
	}
};


int main()
{
	int N, M; cin >> N >> M;
	vector<vector<char>>cho(N);
	int w=0, b=0;
	for (int i = 0; i < N; i++) {
		cho[i].resize(M);
		for (int j = 0; j < M; j++) {
			char c; cin >> c;
			cho[i][j] = c;
			if (c == 'w')w++;
			else if (c == 'b')b++;
		}
	}

	set<int>bs,ws;
	Dinic dn(2502);
	for (int i = 0; i < N; i++) {
		for (int j = 0; j < M; j++) {
			if (cho[i][j] == 'w') {
				ws.insert(i*M + j + 1);
				if (i > 0 && cho[i - 1][j] == 'b') {
					dn.add_edge(i*M + j + 1, (i - 1)*M + j + 1, 1);
					bs.insert((i - 1)*M + j + 1);
				}
				if (i < N - 1 && cho[i + 1][j] == 'b') {
					dn.add_edge(i*M + j + 1, (i + 1)*M + j + 1, 1);
					bs.insert((i + 1)*M + j + 1);
				}
				if (j > 0 && cho[i][j - 1] == 'b') {
					dn.add_edge(i*M + j + 1, i*M + j - 1 + 1, 1);
					bs.insert(i*M + j - 1 + 1);
				}
				if (j < M - 1 && cho[i][j + 1] == 'b') {
					dn.add_edge(i*M + j + 1, i*M + j + 1 + 1, 1);
					bs.insert(i*M + j + 1 + 1);
				}
			}
		}
	}

	for (auto itr = ws.begin(); itr != ws.end(); itr++) {
		dn.add_edge(0, *itr, 1);
	}
	for (auto itr = bs.begin(); itr != bs.end(); itr++) {
		dn.add_edge(*itr, N * M + 1, 1);
	}

	int ans = dn.max_flow(0, N*M+1);
	
	w -= ans;
	b -= ans;

	int pair = min(w,b);
	w -= pair;
	b -= pair;

	cout << ans * 100 + pair * 10 + w + b << endl;

    return 0;
}