// 解説を見て実装

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

using ll = long long;

#define rep(i, n) for (int i=0; i<(int)(n); ++(i))
#define rep3(i, m, n) for (int i=(m); (i)<(int)(n); ++(i))
#define repr(i, n) for (int i=(int)(n)-1; (i)>=0; --(i))
#define rep3r(i, m, n) for (int i=(int)(n)-1; (i)>=(int)(m); --(i))
#define all(x) (x).begin(), (x).end()

int main() {
	int h, w;
	cin >> h >> w;
	map<int, vector<pair<int, int>>> aval;
	rep(i, h) rep(j, w) {
		int ai;
		cin >> ai;
		if (ai == 0) continue;
		aval[ai].emplace_back(i, j);
	}
	int res = 0;
	for (auto p : aval) {
		map<int, int> hid, wid;
		rep(i, (int)(p.second.size())) {
			hid[p.second[i].first] = -1;
			wid[p.second[i].second] = -1;
		}
		auto hitr=hid.begin(), witr=wid.begin();
		for (int j1=0; hitr!=hid.end(); ++hitr,++j1) hitr->second = j1;
		for (int j2=0; witr!=wid.end(); ++witr,++j2) witr->second = j2;
		int n = (int)(hid.size()) + (int)(wid.size());
		mf_graph<int> g(n+2);
		for (auto p2 : hid) g.add_edge(n, p2.second, 1);
		for (auto p2 : wid) g.add_edge((int)(hid.size())+p2.second, n+1, 1);
		rep(i, (int)(p.second.size())) g.add_edge(hid[p.second[i].first], (int)(hid.size())+wid[p.second[i].second], 1);
		res += g.flow(n, n+1);
	}
	cout << res << endl;
	return 0;
}