#include <bits/stdc++.h>
using namespace std;

#ifdef _WIN32
#define scanfll(x) scanf("%I64d", x)
#define printfll(x) printf("%I64d", x)
#else
#define scanfll(x) scanf("%lld", x)
#define printfll(x) printf("%lld", x)
#endif
#define rep(i,n) for(long long i = 0; i < (long long)(n); i++)
#define repi(i,a,b) for(long long i = (long long)(a); i < (long long)(b); i++)
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define fi first
#define se second
#define mt make_tuple
#define mp make_pair
template<class T1, class T2> bool chmin(T1 &a, T2 b) { return b < a && (a = b, true); }
template<class T1, class T2> bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }

using ll = long long; using ld = long double; using vll = vector<ll>; using vvll = vector<vll>; using vld = vector<ld>; 
using vi = vector<int>; using vvi = vector<vi>;
vll conv(vi& v) { vll r(v.size()); rep(i, v.size()) r[i] = v[i]; return r; }
using P = pair<ll, ll>;

template <typename T, typename U> ostream &operator<<(ostream &o, const pair<T, U> &v) {  o << "(" << v.first << ", " << v.second << ")"; return o; }
template<size_t...> struct seq{}; template<size_t N, size_t... Is> struct gen_seq : gen_seq<N-1, N-1, Is...>{}; template<size_t... Is> struct gen_seq<0, Is...> : seq<Is...>{};
template<class Ch, class Tr, class Tuple, size_t... Is>
void print_tuple(basic_ostream<Ch,Tr>& os, Tuple const& t, seq<Is...>){ using s = int[]; (void)s{0, (void(os << (Is == 0? "" : ", ") << get<Is>(t)), 0)...}; }
template<class Ch, class Tr, class... Args> 
auto operator<<(basic_ostream<Ch, Tr>& os, tuple<Args...> const& t) -> basic_ostream<Ch, Tr>& { os << "("; print_tuple(os, t, gen_seq<sizeof...(Args)>()); return os << ")"; }
ostream &operator<<(ostream &o, const vvll &v) { rep(i, v.size()) { rep(j, v[i].size()) o << v[i][j] << " "; cout << endl; } return o; }
template <typename T> ostream &operator<<(ostream &o, const vector<T> &v) { o << '['; rep(i, v.size()) o << v[i] << (i != v.size()-1 ? ", " : ""); o << "]";  return o; }
template <typename T>  ostream &operator<<(ostream &o, const set<T> &m) { o << '['; for (auto it = m.begin(); it != m.end(); it++) o << *it << (next(it) != m.end() ? ", " : ""); o << "]";  return o; }
template <typename T, typename U>  ostream &operator<<(ostream &o, const map<T, U> &m) { o << '['; for (auto it = m.begin(); it != m.end(); it++) o << *it << (next(it) != m.end() ? ", " : ""); o << "]";  return o; }
template <typename T, typename U>  ostream &operator<<(ostream &o, const unordered_map<T, U> &m) { o << '['; for (auto it = m.begin(); it != m.end(); it++) o << *it; o << "]";  return o; }
void printbits(ll mask, ll n) { rep(i, n) { cout << !!(mask & (1ll << i)); } cout << endl; }
#define ldout fixed << setprecision(40) 

static const double EPS = 1e-14;
static const long long INF = 1e18;
static const long long mo = 1e9+7;

struct verticle {
    double theta;
    ll x, y;
    bitset<4> pattern;
};

int main(void) {
    cin.tie(0); ios::sync_with_stdio(false);
    ll hn, wn; cin >> hn >> wn;
    vector<string> b(hn); rep(i, hn) cin >> b[i]; reverse(all(b));

    vector<verticle> vs;
    rep(h, hn+1) rep(w, wn+1) if (h || w) {
        verticle v;
        v.x = h;
        v.y = w;
        v.theta = atan2(h, w);

        // 10 
        // 23
        auto f = [&](ll h, ll w){ return h >= 0 && w >= 0 && h < hn && w < wn; };
        v.pattern[2] = f(h, w-1) && b[h][w-1] == '#';
        v.pattern[0] = f(h-1, w) && b[h-1][w] == '#';
        v.pattern[1] = f(h-1, w-1) && b[h-1][w-1] == '#';
        v.pattern[3] = f(h, w) && b[h][w] == '#'; 
        vs.pb(v);
    }
    sort(all(vs), [](const verticle& a, const verticle& b){ return a.theta < b.theta; });
    /*
    rep(i, vs.size()) {
        cout << vs[i].x << " " << vs[i].y << " " << vs[i].theta << endl;
        cout << vs[i].pattern[1] << vs[i].pattern[0] << endl;
        cout << vs[i].pattern[2] << vs[i].pattern[3] << endl;
    }
    rep(i, b.size()) 
        cout << b[i] << endl;
        */
    ll ret = 0;
    ll cut = 0;
    ll i = 0;
    while (i < vs.size()) {
        /*
        cout << i << endl;
        cout << vs[i].x << " " << vs[i].y << endl;
        */
        double th = vs[i].theta;
        vector<verticle> p;
        while (i < vs.size() && vs[i].theta < th + EPS) {
            p.pb(vs[i]);
            i++;
        }

        rep(j, p.size()) {
            // +1
            if (!p[j].pattern[0] && !p[j].pattern[1] && p[j].pattern[2] && !p[j].pattern[3]) cut++;
            if (p[j].pattern[0] && p[j].pattern[1] && !p[j].pattern[2] && p[j].pattern[3]) cut++;
            // -1
            if (p[j].pattern[0] && !p[j].pattern[1] && !p[j].pattern[2] && !p[j].pattern[3]) cut--;
            if (!p[j].pattern[0] && p[j].pattern[1] && p[j].pattern[2] && p[j].pattern[3]) cut--;
        }
//        cout << cut << endl;
        chmax(ret, cut); 
    }
    cout << ret + 1 << endl;
    return 0;
}

Measured memory_bytes: 20140