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

#define _p(...) (void)printf(__VA_ARGS__)
#define forr(x,arr) for(auto&& x:arr)
#define _overload3(_1,_2,_3,name,...) name
#define _rep2(i,n) _rep3(i,0,n)
#define _rep3(i,a,b) for(int i=int(a);i<int(b);++i)
#define rep(...) _overload3(__VA_ARGS__,_rep3,_rep2,)(__VA_ARGS__)
#define _rrep2(i,n) _rrep3(i,0,n)
#define _rrep3(i,a,b) for(int i=int(b)-1;i>=int(a);i--)
#define rrep(...) _overload3(__VA_ARGS__,_rrep3,_rrep2,)(__VA_ARGS__)
#define all(x) (x).begin(), (x).end()
#define bit(n) (1LL<<(n))
#define sz(x) ((int)(x).size())
#define fst first
#define snd second
using ll=long long;using pii=pair<int,int>;
using vb=vector<bool>;using vs=vector<string>;
using vi=vector<int>;using vvi=vector<vi>;using vvvi=vector<vvi>;
using vl=vector<ll>;using vvl=vector<vl>;using vvvl=vector<vvl>;
using vd=vector<double>;using vvd=vector<vd>;using vvvd=vector<vvd>;
using vpii=vector<pii>;using vvpii=vector<vpii>;using vvvpii=vector<vvpii>;
template<typename T>T read(){T t;cin>>t;return t;}
template<class T,class U>ostream&operator<<(ostream&o,const pair<T,U>&p){o<<'('<<p.fst<<", "<<p.snd<<')';return o;}

template<typename T> bool inside(T y, T x, T h, T w) { return 0 <= y && y < h && 0 <= x && x < w; };
int DY[8] = {1, 0, -1, 0, 1, 1, -1, -1};
int DX[8] = {0, 1, 0, -1, 1, -1, 1, -1};

int enc(vi &m) {
  int ret = 0;
  int n = sz(m);
  rrep(i, n) {
    ret *= 2;
    ret += m[i];
  }
  //cout << "m:"; rep(ii,sz(m)) cout << ' ' << m[ii]; cout << endl;
  //cout << "ret: "<<ret << endl;
  return ret;
}

template<class T> bool amin(T &a, const T &b) { if (b < a) { a = b; return 1; } return 0; }

const int inf = 1e9;

int solve() {
  int h = read<int>();
  int w = read<int>();

  vvi M(h, vi(w));
  rep(y, h) rep(x, w) M[y][x] = read<int>();

  vvvi dp(h+1, vvi(bit(w), vi(bit(w), inf)));

  rep(mask, bit(w)) {
    int st = mask;
    st ^= (mask << 1);
    st ^= (mask >> 1);
    st &= bit(w) - 1;
    amin(dp[0][0][st], __builtin_popcount(mask));
  }

  rep(y, h) {
    rep(c1, bit(w)) {
      rep(c2, bit(w)) if (dp[y][c1][c2] < inf) {
        //_p("dp[%d][%d][%d]: %d\n", y,c1,c2,dp[y][c1][c2]);
        rep(mask, bit(w)) {
          int st = mask;
          st ^= (mask << 1);
          st ^= (mask >> 1);
          st &= bit(w) - 1;
          int e = enc(M[y]);
          int z = e ^ c1 ^ c2 ^ st;
          if (z != 0) continue;
          amin(dp[y+1][c2][st], dp[y][c1][c2] + __builtin_popcount(mask));
        }
      }
    }
  }

  int z = enc(M[h-1]);
  int ans = inf;
  rep(c1, bit(w)) rep(c2, bit(w)) {
    int a = z ^ c1 ^ c2;
    if (a == 0) ans = min(ans, dp[h-1][c1][c2]);
  }

  if (ans >= inf) return -1;
  return ans;
}

void Main() {
  cout << solve() << endl;
}
int main() { cin.tie(nullptr); ios::sync_with_stdio(false); Main(); return 0; }