#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

template<typename T, typename U>
bool chmax(T& a, U b) {
    if (a < b) {
        a = b;
        return true;
    } else {
        return false;
    }
}

template<typename T, typename U>
bool chmin(T& a, U b) {
    if (a > b) {
        a = b;
        return true;
    } else {
        return false;
    }
}

vector<string> rot(vector<string> s, int h, int w) {
    vector<string> res(h);
    for (int i = 0; i < h; ++i) {
        res[i].resize(w);
    }
    for (int i = 0; i < h; ++i) {
        for (int j = 0; j < w; ++j) {
            res[i][j] = s[w - j - 1][i];
        }
    }
    return res;
}

int main()
{
    ll n, m;
    cin >> n >> m;
    vector<vector<string>> s(n, vector<string>(m));
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m; ++j) {
            cin >> s[i][j];
        }
        vector<string> max = s[i];
        for (int j = 0; j < 3; ++j) {
            s[i] = rot(s[i], m, m);
            chmax(max, s[i]);
        }
        s[i] = max;
    }
    ll ans = m * m;
    vector<vector<ll>> grid(m, vector<ll>(m, 0));
    auto f = [&](auto && self, ll cur) -> void {
        if (cur == n) {
            ll ca = 0;
            for (int i = 0; i < m; ++i) {
                for (int j = 0; j < m; ++j) {
                    if (grid[i][j] != 0) ca++;
                }
            }
            chmin(ans, ca);
        } else {
            for (int i = 0; i < 1; ++i) {
                for (int j = 0; j < m; ++j) {
                    for (int k = 0; k < m; ++k) {
                        if (s[cur][j][k] == '#') grid[j][k]++;
                    }
                }
                self(self, cur + 1);
                for (int j = 0; j < m; ++j) {
                    for (int k = 0; k < m; ++k) {
                        if (s[cur][j][k] == '#') grid[j][k]--;
                    }
                }
            }
        }
    };
    f(f, 0);
    cout << ans << endl;
}