#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll=long long;
using ull=unsigned long long;
using ld=long double;
using i128=__int128;
using P=pair<ll,ll>;
template<typename T> using vc=vector<T>;
template<typename T> using vv=vc<vc<T>>;
using vl=vc<ll>;
using vvl=vc<vc<ll>>;
using vul=vc<ull>;
using vs=vc<string>;
using vb=vc<bool>;
#define rep(i,s,n) for(ll i=s;i<(n);i++)
#define Rep(i,s,n) for(ll i=n;i>=s;i--)
#define nall(x) x.begin(),x.end()
#define rall(a) a.rbegin(),a.rend()
#define pb push_back
#define eb emplace_back
#define pob pop_back
#define nexp(v) next_permutation(v)
#define prep(v) prev_permutation(v)
#define YES cout<<"Yes"<<endl
#define NO cout<<"No"<<endl
#define YN {cout<<"Yes"<<endl;}else{cout<<"No"<<endl;}
#define M1 cout<<"-1"<<endl
const long long INF=(1LL<<62)-(1LL<<31)-1;
#define endl '\n'
using mint=modint998244353;
using mint7=modint1000000007;
//vl dx={1,-1,0,0};vl dy={0,0,1,-1};
//vl dx={0,0,1,1,1,-1,-1,-1};vl dy={1,-1,0,1,-1,0,1,-1};
bool out_grid(ll i, ll j, ll h, ll w){return (!(0<=i && i<h && 0<=j && j<w));}
void chmin(ll &a,ll b){if(a>b)a=b;}
void chmax(ll &a,ll b){if(a<b)a=b;}
ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
ll lcm(ll a,ll b){return a/gcd(a,b)*b;}
ll ceil_div(ll a,ll b){return (a+(b-1))/b;}

ll n,m,ans=INF;
vv<vs> pt;
vl rot;

auto rotate90(const vs& g){
	ll h=g.size(),w=g[0].size();
	vs res(w,string(h,'.'));
	rep(i,0,h)rep(j,0,w)res[j][h-1-i]=g[i][j];
	return res;
}

void solve(){
	vs v(m,string(m,'.'));
	rep(i,0,n){
		ll r=rot[i];
		auto &now=pt[i][r];
		rep(j,0,m){
			rep(k,0,m)if(now[j][k]=='#')v[j][k]='#';
		}
	}
	ll cnt=0;
	rep(i,0,m)rep(j,0,m)cnt+=(v[i][j]=='#');
	chmin(ans,cnt);
}

void dfs(ll id){
	if(id==n){
		solve();
		return;
	}
	rep(i,0,4){
		rot[id]=i;
		dfs(id+1);
	}
}

int main(){
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	
	cin >> n >> m;
	pt.resize(n,vv<string>(4));
	rot.resize(n);
	rep(i,0,n){
		vs s(m);
		rep(j,0,m)cin >> s[j];
		pt[i][0]=s;
		pt[i][1]=rotate90(pt[i][0]);
		pt[i][2]=rotate90(pt[i][1]);
		pt[i][3]=rotate90(pt[i][2]);
	}
	dfs(0);
	cout << ans << endl;
}