#include <bits/stdc++.h>
using namespace std;
const int INF = 100000;
template <typename Cap>
struct ford_fulkerson{
	struct edge{
		int to, rev;
		Cap cap;
		edge(int to, int rev, Cap cap): to(to), rev(rev), cap(cap){
		}
	};
	int N;
	vector<vector<edge>> G;
	ford_fulkerson(){
	}
	ford_fulkerson(int N): N(N), G(N){
	}
	void add_edge(int from, int to, Cap cap){
		int id1 = G[from].size();
		int id2 = G[to].size();
		G[from].push_back(edge(to, id2, cap));
		G[to].push_back(edge(from, id1, 0));
	}
	Cap max_flow(int s, int t){
		Cap flow = 0;
		while (1){
			vector<Cap> m(N, INF);
			vector<int> pv(N, -1);
			vector<int> pe(N, -1);
			vector<bool> used(N, false);
			queue<int> Q;
			Q.push(s);
			used[s] = true;
			while (!Q.empty()){
				int v = Q.front();
				Q.pop();
				int cnt = G[v].size();
				for (int i = 0; i < cnt; i++){
					int w = G[v][i].to;
					if (!used[w] && G[v][i].cap > 0){
						used[w] = true;
						m[w] = min(m[v], G[v][i].cap);
						pv[w] = v;
						pe[w] = i;
						Q.push(w);
					}
				}
			}
			if (!used[t]){
				break;
			}
			Cap f = m[t];
			for (int i = t; i != s; i = pv[i]){
				G[pv[i]][pe[i]].cap -= f;
				G[i][G[pv[i]][pe[i]].rev].cap += f;
			}
			flow += f;
		}
		return flow;
	}
};
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();
    }
    ford_fulkerson<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.max_flow(Xcnt + Ycnt, Xcnt + Ycnt + 1);
  }
  cout << ans << endl;
}