// yukicoder: No.421 しろくろチョコレート
// bal4u 2019.8.18

#include <stdio.h>
#include <string.h>

//// 入出力関係
#if 1
#define gc() getchar_unlocked()
#else
#define gc() getchar()
#endif

int in() { // 非負整数の入力
	int n = 0, c = gc();
	do n = 10 * n + (c & 0xf); while ((c = gc()) >= '0');
	return n;
}

void ins(char *s) { // 文字列の入力　スペース以下の文字で入力終了
	char *p = s;
	do *s = gc();
	while (*s++ > ' ');
	*--s = 0;
}

//// 二部マッチング
#define MAX 2600
int  V;
int  hi[MAX], to[MAX][8];
char seen[MAX];
int  match[MAX];

int bpm(int u);
int bipartiteMatching(int m)
{
	int u, max;

	memset(match, -1, sizeof(match));
	max = 0;
	for (u = 0; u < m; u++) {
		memset(seen, 0, sizeof(seen));
		if (bpm(u)) max++;
	}
	return max;
}

int bpm(int u)
{
	int i, v;

	for (i = 0; i < hi[u]; i++) {
		v = to[u][i];
		if (seen[v]) continue;
		seen[v] = 1;
		if (match[v] < 0 || bpm(match[v])) {
			match[u] = v, match[v] = u;
			return 1;
		}
	}
	return 0;
}

//// 本問題関連
int H, W;
char map[53][53];
#define MIN(a,b)  ((a)<=(b)?(a):(b))
#define rc2id(r, c)  ((r)*W+(c))
int mv[4][2] = {{-1,0},{0,1},{1,0},{0,-1}};

int main()
{
	int i, r, c, t, rr, cc, tt, w, b, ans;

	H = in(), W = in();
	w = b = 0; for (r = 0; r < H; r++) {
		ins(map[r]);
		for (c = 0; c < W; c++) {
			if (map[r][c] == 'w') w++;
			else if (map[r][c] == 'b') b++;
		}
	}
	
	if ((w | b) == 0) ans = 0;
	else if ((w & b) == 0) ans = w + b;
	else {
		for (r = 0; r < H; r++) for (c = r&1; c < W; c+=2) if (map[r][c] == 'w') {
			t = rc2id(r, c);
			for (i = 0; i < 4; i++) {
				rr = r+mv[i][0], cc = c+mv[i][1];
				if (rr >= 0 && rr < H && cc >= 0 && cc < W && map[rr][cc] == 'b') {
					tt = rc2id(rr, cc), to[tt][hi[tt]++] = t;
				}
			}
		}
	
		t = bipartiteMatching(H*W);
		w -= t, b -= t, ans = 100 * t;
		t = MIN(w, b), 	ans += 10 * t;
		w -= t, b -= t, ans += w + b;
	}
	printf("%d\n", ans);
	return 0;
}