package yukicoder;

import java.util.Scanner;
import java.util.List;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;

public class No1479_2 {
	
	private static class Values {
		public HashMap<Integer, Integer> di, dj;
		public List<Integer[]> ij;
		public Values() {
			di = new HashMap<Integer, Integer> ();
			dj = new HashMap<Integer, Integer> ();
			ij = new ArrayList<Integer[]>();
		}
	}
	
	private static int V;
	private static int[] match;
	private static boolean[] used;
	private static List<List<Integer>> G;
	
	private static void add_edge(int u, int v) {
		G.get(u).add(v);
		G.get(v).add(u);
	}

	private static boolean dfs(int v) {
		used[v] = true;
		for (int u : G.get(v)) {
			int w = match[u];
			if (w < 0 || !used[w] && dfs(w)) {
				match[v] = u;
				match[u] = v;
				return true;
			}
		}
		return false;
	}
	
	private static int bipartite_matching() {
		int res = 0;
		match = new int[V];
		Arrays.fill(match, -1);
		for (int v=0; v < V; v++) {
			if (match[v] < 0) {
				used = new boolean[V];
				if (dfs(v)) {
					res++;
				}
			}
		}
		return res;
	}
	
	private static int mpc(int h, int w) {
		int res = bipartite_matching();
		List<Integer> matched = new ArrayList<Integer>();
		for (int i=h; i < h+w; i++) {
			matched.add(match[i]);
		}
		int left = h, right = 0;
		for (int v = 0; v < h; v++) {
			if (!matched.contains(v)) {
				left--;
				for (int u : G.get(v)) {
					right++;
					if (match[u] >= 0) {
						left--;
					}
				}
			}
		}
		return left + right;
	}
	
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int H = scan.nextInt();
		int W = scan.nextInt();
		HashMap<Integer, Values> S = new HashMap<Integer, Values>();
		for (int i=0; i < H; i++) {
			for (int j=0; j < W; j++) {
				int a = scan.nextInt();
				if (a > 0) {
					if (!S.containsKey(a)) {
						Values v = new Values();
						v.di.put(i, 0);
						v.dj.put(j, 0);
						v.ij.add(new Integer[] {0, 0});
						S.put(a, v);
					} else {
						Values v = S.get(a);
						int ai, aj;
						if (v.di.containsKey(i)) {
							ai = v.di.get(i);
						} else {
							ai = v.di.size();
							v.di.put(i, ai);
						}
						if (v.dj.containsKey(j)) {
							aj = v.dj.get(j);
						} else {
							aj = v.dj.size();
							v.dj.put(j, aj);
						}
						v.ij.add(new Integer[] {ai, aj});
					}
				}
			}
		}
		scan.close();
		int cnt = 0;
		for (Values v : S.values()) {
			int h = v.di.size();
			int w = v.dj.size();
			V = h + w;
			G = new ArrayList<List<Integer>>();
			for (int i=0; i < V; i++) {
				G.add(new ArrayList<Integer>());
			}
			for (Integer[] i : v.ij) {
				add_edge(i[0], i[1]+h);
			}
			int n = mpc(h, w);
			cnt += n;
		}
		System.out.println(cnt);
	}

}