#include "bits/stdc++.h"
using namespace std;
typedef long long int lint;
typedef pair<lint, lint> plint;
typedef pair<double long, double long> pld;
#define Alint(x) (x).begin(), (x).end()
#define SZ(x) ((lint)(x).size())
#define POW2(n) (1ll << (n))
#define FOR(i, begin, end) for(lint i=(begin),i##_end_=(end);i<i##_end_;i++)
#define IFOR(i, begin, end) for(lint i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
template<class T>bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }
template<typename T1, typename T2> pair<T1, T2> operator+(const pair<T1, T2>& l, const pair<T1, T2>& r) { return make_pair(l.first + r.first, l.second + r.second); }
template<typename T1, typename T2> pair<T1, T2> operator-(const pair<T1, T2>& l, const pair<T1, T2>& r) { return make_pair(l.first - r.first, l.second - r.second); }
const lint MOD = 998244353, INF = 1e9;

template<typename flow_t, typename cost_t>
struct Flow {
	const cost_t INF = pow(10, 18);
	struct edge {
		lint to;
		flow_t cap;
		cost_t cost;
		lint rev;
	};
	vector<vector<edge> > Graph;
	vector<cost_t> potential, min_cost;
	vector<lint> prevv, preve;
	vector<lint> level;
	vector<lint> iter;

	Flow(lint V) :Graph(V) {}

	void add_edge(lint from, lint to, flow_t cap, cost_t cost = 0) {
		Graph[from].push_back({ to, cap, cost, SZ(Graph[to]) });
		Graph[to].push_back({ from, 0, -cost, SZ(Graph[from]) - 1 });
	}

	void bfs(lint s) {
		lint V = SZ(Graph);
		level.assign(V, -1);
		queue<lint> que;
		que.push(s);
		level[s] = 0;
		while (!que.empty()) {
			lint v = que.front(); que.pop();
			REP(i, SZ(Graph[v])) {
				edge& e = Graph[v][i];
				if (e.cap > 0 && level[e.to] < 0) {
					level[e.to] = level[v] + 1;
					que.push(e.to);
				}
			}
		}
	}

	flow_t dfs(lint v, lint t, flow_t f) {
		if (v == t) return f;
		for (lint& i = iter[v]; i < SZ(Graph[v]); i++) {
			edge& e = Graph[v][i];
			if (e.cap > 0 && level[v] < level[e.to]) {
				flow_t d = dfs(e.to, t, min(f, e.cap));
				if (d > 0) {
					e.cap -= d;
					Graph[e.to][e.rev].cap += d;
					return d;
				}
			}
		}
		return 0;
	}

	flow_t max_flow(lint s, lint t) {
		flow_t flow = 0;
		lint V = SZ(Graph);
		for (;;) {
			bfs(s);
			if (level[t] < 0) return flow;
			iter.assign(V, 0);
			flow_t f;
			while ((f = dfs(s, t, INF)) > 0) {
				flow += f;
			}
		}
	}

	lint min_cost_flow(lint s, lint t, lint f) {
		cost_t res = 0;
		lint V = SZ(Graph);

		potential.assign(V, 0);
		prevv.assign(V, -1);
		preve.assign(V, -1);

		while (f > 0) {
			priority_queue<pair<cost_t, lint>, vector<pair<cost_t, lint> >, greater<pair<cost_t, lint> > > que;
			min_cost.assign(V, INF);
			min_cost[s] = 0;
			que.push({ 0, s });
			while (!que.empty()) {
				pair<cost_t, lint> p = que.top(); que.pop();
				lint v = p.second;
				if (min_cost[v] < p.first) continue;
				REP(i, SZ(Graph[v])) {
					edge& e = Graph[v][i];
					cost_t nextCost = min_cost[v] + e.cost + potential[v] - potential[e.to];
					if (e.cap > 0 && min_cost[e.to] > nextCost) {
						min_cost[e.to] = nextCost;
						prevv[e.to] = v;
						preve[e.to] = i;
						que.push({ min_cost[e.to], e.to });
					}
				}
			}
			if (min_cost[t] == INF) {
				return -1;
			}
			REP(v, V) potential[v] += min_cost[v];

			flow_t addflow = f;
			for (lint v = t; v != s; v = prevv[v]) {
				addflow = min(addflow, Graph[prevv[v]][preve[v]].cap);
			}
			f -= addflow;
			res += addflow * potential[t];
			for (lint v = t; v != s; v = prevv[v]) {
				edge& e = Graph[prevv[v]][preve[v]];
				e.cap -= addflow;
				Graph[v][e.rev].cap += addflow;
			}
		}
		return res;
	}
};

lint H, W;
char char_map[50][50];
int main() {
	cin.tie(0); ios_base::sync_with_stdio(false);
	cin >> H >> W;
	lint s = H * W, t = s + 1;
	Flow<lint, lint> g(t + 1);
	lint white_cnt = 0, black_cnt = 0;
	REP(i, H) {
		REP(j, W) {
			cin >> char_map[i][j];
			if (char_map[i][j] == 'b') black_cnt++;
			else if(char_map[i][j] == 'w') white_cnt++;
		}
	}
	REP(i, H) {
		REP(j, W) {
			lint idx = i * W + j;
			if (char_map[i][j] == 'b') {
				g.add_edge(idx, t, 1);
			}
			if (char_map[i][j] == 'w') {
				g.add_edge(s, idx, 1);
				lint dx[4] = { 0, 1, 0, -1 }, dy[4] = { 1, 0, -1, 0 };
				REP(k, 4) {
					lint ny = i + dy[k], nx = j + dx[k];
					if (nx >= 0 && ny >= 0 && nx < W && ny < H && char_map[ny][nx] == 'b') {
						g.add_edge(idx, ny * W + nx, 1);
					}
				}
			}
		}
	}
	lint match = g.max_flow(s, t);
	white_cnt -= match; black_cnt -= match;
	lint unmatch = min(white_cnt, black_cnt);
	white_cnt -= unmatch; black_cnt -= unmatch;
	cout << match * 100 + unmatch * 10 + white_cnt + black_cnt << endl;
}