import collections
import sys
sys.setrecursionlimit(10 ** 6)
input = sys.stdin.readline


def dfs(v, left, right, used, g):
    if v in used: return False
    used.add(v)
    for u in g[v]:
        if right[u] == -1 or dfs(right[u], left, right, used, g):
            right[u] = v
            left[v] = u
            return True
    return False


def max_bipartite_matching(n, m, g):
    res = 0
    left = [-1] * n
    right = [-1] * m
    used = set()
    update = True
    while update:
        update = False
        for i in range(len(left)):
            if left[i] == -1 and dfs(i, left, right, used, g):
                update = True
                res += 1
        if update:
            used = set()
    return res, left, right


N, M = map(int, input().split())
g = [input() for _ in range(N)]

w = b = 0
adj = collections.defaultdict(list)
for i in range(N):
    w += g[i].count('w')
    b += g[i].count('b')
    for j in range(M):
        if (i + j) % 2 == 1: continue
        for dr, dc in [(1, 0), (-1, 0), (0, 1), (0, -1)]:
            r = i + dr
            c = j + dc
            if 0 <= r < N and 0 <= c < M:
                if sorted([g[i][j], g[r][c]]) == ['b', 'w']:
                    p = i * M + j
                    q = r * M + c
                    adj[p].append(q)

cnt, _, _ = max_bipartite_matching(N * M, N * M, adj)
w -= cnt
b -= cnt
k = min(w, b)
ans = cnt * 100 + k * 10 + (w - k) + (b - k)
print(ans)