from collections import deque
import sys
input = sys.stdin.readline
sys.setrecursionlimit(10 ** 7)
DX = (-1, 0, 1, 0, -1, -1, 1, 1)
DY = (0, 1, 0, -1, -1, 1, -1, 1)
DX = DX[:4]
DY = DY[:4]


class MF_graph(object):
    def __init__(self, n):
        self.n = n
        self.g = [[] for _ in range(n)]  # to, rev, cap
        self.pos = []

    def add_edge(self, frm, to, cap):
        """ frmからtoへ容量cap, 流量0の辺を追加, 何番目の辺かを返す"""
        m = len(self.pos)
        self.pos.append((frm, len(self.g[frm])))
        self.g[frm].append([to, len(self.g[to]), cap])
        self.g[to].append([frm, len(self.g[frm]) - 1, 0])
        return m

    def get_edge(self, i):
        e_to, e_rev, e_cap = self.g[self.pos[i][0]][self.pos[i][1]]
        re_to, _, re_cap = self.g[e_to][e_rev]
        # from, to, cap, flow
        return (re_to, e_to, e_cap + re_cap, re_cap)

    def edges(self):
        m = len(self.pos)
        for i in range(m):
            yield self.get_edge(i)

    def change_edge(self, i, new_cap, new_flow):
        """ i番目に追加された辺の容量,流量をnew_cap, new_flowに変更する """
        f, s = self.pos[i]
        rf, rs, _ = self.g[f][s]
        self.g[f][s][2] = new_cap - new_flow
        self.g[rf][rs][2] = new_flow
        return

    def __dfs(self, s, v, up):
        if v == s:
            return up
        res = 0
        level_v = self.level[v]
        for i in range(self.iter[v], len(self.g[v])):
            u_to, u_rev, _ = self.g[v][i]
            if level_v <= self.level[u_to] or self.g[u_to][u_rev][2] == 0:
                continue
            d = self.__dfs(s, u_to, min(up - res, self.g[u_to][u_rev][2]))
            if d <= 0:
                continue
            self.g[v][i][2] += d
            self.g[u_to][u_rev][2] -= d
            res += d
            if res == up:
                break
        return res

    def flow(self, s, t, flow_limit=10**18):
        """ sからtへflow_limitだけ流す。流せた量を返す """
        self.iter = [0] * self.n
        flow = 0
        while flow < flow_limit:
            self.level = [-1] * self.n
            self.level[s] = 0
            que = deque([s])
            while que:
                v = que.popleft()
                for u_to, _, u_cap in self.g[v]:
                    if u_cap == 0 or self.level[u_to] >= 0:
                        continue
                    self.level[u_to] = self.level[v] + 1
                    if u_to == t:
                        break
                    que.append(u_to)

            if self.level[t] == -1:
                break
            self.iter = [0] * self.n
            while flow < flow_limit:
                f = self.__dfs(s, t, flow_limit - flow)
                if not f:
                    break
                flow += f
        return flow

    def min_cut(self, s):
        """ 最小カットを返す。sから到達可能だとTrue """
        visited = [False] * self.n
        que = deque([s])
        while que:
            v = que.popleft()
            visited[v] = True
            for u_to, _, u_cap in self.g[v]:
                if u_cap and (not visited[u_to]):
                    visited[u_to] = True
                    que.append(u_to)
        return visited


N, M = map(int, input().split())
S = [input().rstrip() for _ in range(N)]
source = N * M
sink = source + 1

G = MF_graph(N * M + 2)
black = 0
white = 0
for x in range(N):
    for y in range(M):
        if S[x][y] == ".":
            continue
        if (x + y) % 2 == 0:
            white += 1
            G.add_edge(source, x * M + y, 1)
            for dx, dy in zip(DX, DY):
                nx = x + dx
                ny = y + dy
                if 0 <= nx < N and 0 <= ny < M and S[nx][ny] != ".":
                    G.add_edge(x * M + y, nx * M + ny, 1)
        else:
            black += 1
            G.add_edge(x * M + y, sink, 1)

ans = 0
flow = G.flow(source, sink)
ans += 100 * flow

black -= flow
white -= flow
d = min(black, white)
ans += 10 * d

black -= d
white -= d
ans += black + white

print(ans)