#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9+10;
const ll INF=4e18;
const ll dy[9]={1,0,-1,0,1,1,-1,-1,0};
const ll dx[9]={0,1,0,-1,1,-1,1,-1,0};
template <typename T> inline bool chmax(T &a, T b) {
  return ((a < b) ? (a = b, true) : (false));
}
template <typename T> inline bool chmin(T &a, T b) {
  return ((a > b) ? (a = b, true) : (false));
}
int main(){
  ll h,w;cin >> h >> w;
  vvl g(h,vl(w));rep(i,h)rep(j,w)cin >> g[i][j];
  ll ans=INF;
  rep(bit,1<<h){
    rep(cit,1<<w){
      vvl ng=g;
      ll cost=0;
      rep(i,h){
        if(bit>>i&1){
          cost++;
          rep(k,9){
            ll x=i+dx[k],y=dy[k];
            if(x<0||y<0||x>=h||y>=w)continue;
            ng[x][y]^=1;
          }
        }
      }
      rep(i,w){
        if(cit>>i&1){
          cost++;
          rep(k,9){
            ll x=dx[k],y=i+dy[k];
            if(x<0||y<0||x>=h||y>=w)continue;
            ng[x][y]^=1;
          }
        }
      }
      rep(i,h-1){
        rep(j,w-1){
          if(ng[i][j]==0)continue;
          cost++;
          rep(k,9){
            ll x=i+1+dx[k],y=j+1+dy[k];
            if(x<0||y<0||x>=h||y>=w)continue;
            ng[x][y]^=1;
          }
        }
      }
      bool ok=true;
      rep(i,h)rep(j,w)if(ng[i][j]==1)ok=false;
      if(ok)chmin(ans,cost);
    }
  }
  cout << ans << endl;
}