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

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N,M; cin >> N >> M;
    vector<vector<string>> Ss(N,vector<string>(M));
    for(auto &S : Ss) for(auto &s : S) cin >> s;

    auto rot = [&](vector<string> &S) -> void {
        vector<string> T(M,string(M,'.'));
        for(int i=0; i<M; i++) for(int k=0; k<M; k++) T.at(k).at(M-1-i) = S.at(i).at(k);
        swap(S,T);
    };
    int answer = 1001001001;
    auto check = [&]() -> void {
        vector<vector<bool>> B(M,vector<bool>(M));
        for(int i=0; i<N; i++) for(int x=0; x<M; x++) for(int y=0; y<M; y++) if(Ss.at(i).at(x).at(y) == '#') B.at(x).at(y) = true;
        int now = 0;
        for(int x=0; x<M; x++) for(int y=0; y<M; y++) now += B.at(x).at(y);
        answer = min(answer,now);
    };
    auto dfs = [&](auto dfs,int pos) -> void {
        if(pos == N){check(); return;}
        for(int i=0; i<4; i++) dfs(dfs,pos+1),rot(Ss.at(pos));
    };
    dfs(dfs,0);
    cout << answer << endl;

}