#include <bits/stdc++.h>
#include <atcoder/maxflow>
using namespace std;
using namespace atcoder;
int main(){
  int H, W;
  cin >> H >> W;
  vector<vector<int>> A(H, vector<int>(W));
  for (int i = 0; i < H; i++){
    for (int j = 0; j < W; j++){
      cin >> A[i][j];
    }
  }
  map<int, vector<pair<int, int>>> mp;
  for (int i = 0; i < H; i++){
    for (int j = 0; j < W; j++){
      if (A[i][j] > 0){
        mp[A[i][j]].push_back(make_pair(i, j));
      }
    }
  }
  int ans = 0;
  for (auto P : mp){
    int cnt = P.second.size();
    vector<int> X, Y;
    for (int i = 0; i < cnt; i++){
      X.push_back(P.second[i].first);
      Y.push_back(P.second[i].second);
    }
    sort(X.begin(), X.end());
    X.erase(unique(X.begin(), X.end()), X.end());
    sort(Y.begin(), Y.end());
    Y.erase(unique(Y.begin(), Y.end()), Y.end());
    int Xcnt = X.size(), Ycnt = Y.size();
    vector<int> x(cnt), y(cnt);
    for (int i = 0; i < cnt; i++){
      x[i] = lower_bound(X.begin(), X.end(), P.second[i].first) - X.begin();
      y[i] = lower_bound(Y.begin(), Y.end(), P.second[i].second) - Y.begin();
    }
    mf_graph<int> G(Xcnt + Ycnt + 2);
    for (int i = 0; i < Xcnt; i++){
      G.add_edge(Xcnt + Ycnt, i, 1);
    }
    for (int i = 0; i < Ycnt; i++){
      G.add_edge(Xcnt + i, Xcnt + Ycnt + 1, 1);
    }
    for (int i = 0; i < cnt; i++){
      G.add_edge(x[i], Xcnt + y[i], 1);
    }
    ans += G.flow(Xcnt + Ycnt, Xcnt + Ycnt + 1);
  }
  cout << ans << endl;
}