#include <bits/stdc++.h>
using namespace std;
using ll=long long;
using pint=pair<int,int>;
#define rep(i,n) for(int i=0;i<(n);++i)
template<typename T>
void chmax(T& a,T b){if(a<b){a=b;};}
template<typename T>
void chmin(T& a,T b){if(a>b){a=b;};}
const int inf=1e9;

template<typename T>
void rotate(vector<vector<T>>& ary,bool rev=false){
  int n=ary.size(),m=ary[0].size();
  vector copy(m,vector<T>(n));
  rep(i,n)rep(j,m){
    if(!rev)copy[j][n-i-1]=ary[i][j];
    else copy[m-j-1][i]=ary[i][j];
  }
  ary=copy;
}

int main(){
  int n,m;cin>>n>>m;
  vector s(n,vector<vector<char>>(m,vector<char>(m)));
  rep(i,n)rep(j,m)rep(k,m)cin>>s[i][j][k];
  int ans=inf;
  auto f=[&](auto self,int depth,vector<vector<char>> grid)->void{
    if(depth==n){
      int cnt=0;
      rep(i,m)rep(j,m)cnt+=grid[i][j]=='#';
      chmin(ans,cnt);
      return;
    }
    rep(i,4){
      auto ngrid=grid;
      rep(j,m)rep(k,m)if(s[depth][j][k]=='#')ngrid[j][k]='#';
      self(self,depth+1,ngrid);
      rotate(s[depth]);
    }
  };
  vector grid(m,vector<char>(m,'.'));
  f(f,0,grid);
  cout<<ans<<endl;
}