#include "bits/stdc++.h"
//#include "atcoder/all"
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
struct BipartiteMatching {
	vector< vector< int > > graph;
	vector< int > match, alive, used;
	int timestamp;

	BipartiteMatching(int n) : graph(n), alive(n, 1), used(n, 0), match(n, -1), timestamp(0) {}

	void add_edge(int u, int v) {
		graph[u].push_back(v);
		graph[v].push_back(u);
	}

	bool dfs(int idx) {
		used[idx] = timestamp;
		for (auto &to : graph[idx]) {
			int to_match = match[to];
			if (alive[to] == 0) continue;
			if (to_match == -1 || (used[to_match] != timestamp && dfs(to_match))) {
				match[idx] = to;
				match[to] = idx;
				return true;
			}
		}
		return false;
	}

	int bipartite_matching() {
		int ret = 0;
		for (int i = 0; i < graph.size(); i++) {
			if (alive[i] == 0) continue;
			if (match[i] == -1) {
				++timestamp;
				ret += dfs(i);
			}
		}
		return ret;
	}

	void output() {
		for (int i = 0; i < graph.size(); i++) {
			if (i < match[i]) {
				cout << i << "-" << match[i] << endl;
			}
		}
	}
};
#define P pair<int,int>
vector<P>v[500005];
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int h, w;  cin >> h >> w;
	rep(i, h) rep(j, w) {
		int a; cin >> a;
		v[a].push_back({ i,j });
	}
	int ans = 0;
	rep(i, 500001) {
		if (0 == i) continue;
		if (v[i].empty()) continue;
		set<int>st;
		for (auto p : v[i]) {
			st.insert(p.first);
			st.insert(p.second + h);
		}
		map<int, int>mp;
		for (auto s : st) {
			mp[s] = mp.size();
		}
		//二部グラフの二部グラフの最大マッチング　＝　最小頂点被覆
		BipartiteMatching g(mp.size());
		for (auto p : v[i]) {
			g.add_edge(mp[p.first], mp[p.second + h]);
		}
		ans += g.bipartite_matching();
	}
	cout << ans << endl;
	return 0;
}