#include <bits/stdc++.h>
using namespace std;
#if __has_include(<atcoder/all>)
#include <atcoder/all>
using namespace atcoder;
#endif
using ll = long long;
using ld = long double;
#define all(s) (s).begin(),(s).end()
#define vcin(n) for(ll i=0;i<ll(n.size());i++) cin>>n[i]
#define rep2(i, m, n) for (int i = (m); i < (n); ++i)
#define rep(i, n) rep2(i, 0, n)
#define drep2(i, m, n) for (int i = (m)-1; i >= (n); --i)
#define drep(i, n) drep2(i, n, 0)
#define rever(vec) reverse(vec.begin(), vec.end())
#define sor(vec) sort(vec.begin(), vec.end())
#define fi first
#define se second
#define P pair<ll,ll>
const ll mod = 998244353;
//const ll mod = 1000000007;
const ll inf = 2000000000000000000ll;
static const long double pi = 3.141592653589793;
void YesNo(bool a){if(a){cout<<"Yes"<<endl;}else{cout<<"No"<<endl;}}
void YESNO(bool a){if(a){cout<<"YES"<<endl;}else{cout<<"NO"<<endl;}}
template<class T,class U> void chmax(T& t,const U& u){if(t<u) t=u;}
template<class T,class U> void chmin(T& t,const U& u){if(t>u) t=u;}
ll modPow(ll a, ll n, ll mod) { ll ret = 1; ll p = a % mod; while (n) { if (n & 1) ret = ret * p % mod; p = p * p % mod; n >>= 1; } return ret; }

int main() {
  /* mod は 1e9+7 */
  ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
  cout<< fixed << setprecision(10);
  ll a,b;
  cin>>a>>b;
  unordered_map<ll,vector<pair<ll,ll>>> m;
  for(int i=0;i<a;i++){
    for(int j=0;j<b;j++){
      ll t;
      cin>>t;
      if(t){
        m[t].emplace_back(i,j);
      }
    }
  }
  ll ans=0;
  for(auto &x:m){
    unordered_map<ll,ll> p,q;
    ll u=1,v=1;
    for(auto &y:x.se){
      if(p[y.fi]==0){
        p[y.fi]=u;
        u++;
      }
      if(q[y.se]==0){
        q[y.se]=v;
        v++;
      }
    }
    mf_graph<ll> g(u+v+2);
    for(int j=0;j<u;j++){
      g.add_edge(u+v,j,1);
    }
    for(int j=0;j<v;j++){
      g.add_edge(u+j,u+v+1,1);
    }
    for(auto &h:x.se){
      g.add_edge(p[h.fi]-1,u+q[h.se]-1,1);
    }
    ans+=g.flow(u+v,u+v+1);
  }
  cout<<ans<<endl;
}