/* -*- coding: utf-8 -*-
 *
 * 1479.cc:  No.1479 Matrix Eraser - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_H = 500;
const int MAX_W = 500;
const int MAX_N = MAX_H * MAX_W;
const int MAX_M = MAX_H + MAX_W;

/* typedef */

typedef vector<int> vi;
typedef vector<bool> vb;
typedef map<int,int> mii;


struct Elm {
  int a, i, j;
  Elm() {}
  Elm(int _a, int _i, int _j): a(_a), i(_i), j(_j) {}
  bool operator<(const Elm &e) const { return a < e.a; }
  bool operator>(const Elm &e) const { return a > e.a; }
};

/* global variables */

int as[MAX_H][MAX_W];
Elm es[MAX_N];
mii hls, vls;
vi nbrs[MAX_M];

/* subroutines */

bool max_match_rec(const vi *nbrs, int u, vi &matches, vb &visited) {
  if (u < 0) return true;
  const vi &nbru = nbrs[u];
  for (vi::const_iterator vit = nbru.begin(); vit != nbru.end(); vit++) {
    const int &v = *vit;
    if (! visited[v]) {
      visited[v] = true;
      if (max_match_rec(nbrs, matches[v], matches, visited)) {
	matches[u] = v;
	matches[v] = u;
	return true;
      }
    }
  }
  return false;
}

int max_match(const int n, int l, const vi *nbrs) {
  vi matches(n, -1);
  int count = 0;
  
  for (int u = 0; u < l; u++) {
    vb visited(n, false);
    if (max_match_rec(nbrs, u, matches, visited)) count++;
  }

  return count;
}

/* main */

int main() {
  int h, w;
  scanf("%d%d", &h, &w);

  int n = 0;
  for (int i = 0; i < h; i++)
    for (int j = 0; j < w; j++) {
      scanf("%d", as[i] + j);
      if (as[i][j] > 0) es[n++] = Elm(as[i][j], i, j);
    }
  sort(es, es + n, greater<Elm>());

  int sum = 0;
  for (int k0 = 0; k0 < n;) {
    int k1 = k0 + 1;
    while (k1 < n && es[k0].a == es[k1].a) k1++;

    if (k0 + 1 == k1) sum++;
    else {
      hls.clear(), vls.clear();
      int hm = 0, vm = 0;
      for (int k = k0; k < k1; k++) {
	mii::iterator mit0 = hls.find(es[k].i);
	if (mit0 == hls.end()) hls[es[k].i] = hm++;
	mii::iterator mit1 = vls.find(es[k].j);
	if (mit1 == vls.end()) vls[es[k].j] = vm++;
      }

      int m = hm + vm;
      for (int i = 0; i < m; i++) nbrs[i].clear();
      for (int k = k0; k < k1; k++) {
	int ki = hls[es[k].i], kj = vls[es[k].j] + hm;
	nbrs[ki].push_back(kj);
	nbrs[kj].push_back(ki);
      }

      int cnt = max_match(m, hm, nbrs);
      //printf("%d: %d,%d\n", es[k0].a, k1 - k0, cnt);
      sum += cnt;
    }

    k0 = k1;
  }

  printf("%d\n", sum);
  return 0;
}