#include <algorithm>
#include <cassert>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <iostream>
#include <numeric>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <functional>
#include <iomanip>
using namespace std;
using ll = long long;

class range {private: struct I{int x;int operator*(){return x;}bool operator!=(I& lhs){return x<lhs.x;}void operator++(){++x;}};I i,n;
public:range(int n_):i({0}),n({n_}){}range(int i_,int n_):i({i_}),n({n_}){}I& begin(){return i;}I& end(){return n;}};

template<typename T, typename U> ostream& operator<<(ostream& os, const pair<T, U>& p){ return os << "{" << p.first << ", " << p.second << "}"; }
template<typename T> ostream& operator<<(ostream& os, const vector<T>& obj) { os << "{"; for (const auto& e : obj) os << e << ", "; return os << "}"; }
template<typename T> ostream& operator<<(ostream& os, const set<T>& obj) { os << "set{"; for (const auto& e : obj) os << e << ", "; return os << "}"; }
template<typename T, typename U> ostream& operator<<(ostream& os, const map<T, U>& obj) { os << "map{"; for (const auto& e : obj) os << e << ", "; return os << "}"; }
template<typename T> void take(vector<T>& vec, int n) { vec.resize(n); for (int i = 0; i < n; ++i) cin >> vec[i]; }

#ifdef ONLINE_JUDGE
#define dump(expr) ;
#else
#define dump(expr) { cerr << "\033[33m#L" << __LINE__ << ": " << expr << "\033[39m" << endl; }
#endif

using EdgeCost = ll;
struct E {
  int fr, to, eid; EdgeCost cost;
  E(int fr_, int to_, int eid_, EdgeCost cost_) : fr(fr_), to(to_), eid(eid_), cost(cost_) {}
  friend ostream &operator<<(ostream &os, const E &e) { os << "(" << e.fr << " -> " << e.to << ")"; return os; }
};
using V = vector<E>;
struct G {
  int n, e_count;
  vector<V> adj, rev;
  G(int n_) : n(n_), e_count(0), adj(n), rev(n) {}

  void add_directed_edge(int fr, int to, EdgeCost cost = (EdgeCost)1) {
    assert(0 <= fr && fr < n); assert(0 <= to && to < n); E e(fr, to, e_count++, cost); adj[fr].push_back(e); rev[to].push_back(e);
  }
  void add_undirected_edge(int fr, int to, EdgeCost cost = (EdgeCost)1) {
    assert(0 <= fr && fr < n); assert(0 <= to && to < n); E e1(fr, to, e_count, cost), e2(to, fr, e_count++, cost);
    adj[fr].push_back(e1); rev[to].push_back(e1); adj[to].push_back(e2); rev[to].push_back(e2);
  }
};

struct BipartiteMatching {
  const int INFTY = numeric_limits<int>::max() / 2;

  int nil;
  vector<int> pair_val;
  vector<int> dist_val;

  bool dfs(G &g, int j) {
    if (j == nil) return true;

    for (auto e : g.adj[j]) {
      if (dist_val[pair_val[e.to]] == dist_val[j] + 1 && dfs(g, pair_val[e.to])) {
        pair_val[e.to] = j;
        pair_val[j] = e.to;
        return true;
      }
    }
    dist_val[j] = INFTY;
    return false;
  }

  int exec(G &g, int n1, int n2) {
    // left vertices:  [0, n1)
    // right vertices: [n1, n1 + n2)
    assert((int)g.adj.size() == n1 + n2);
    nil = n1 + n2;
    pair_val.assign(n1 + n2 + 1, nil);

    int res = 0;
    for (;;) {
      queue<int> q;
      dist_val.assign(n1 + n2 + 1, INFTY);

      for (int j : range(n1 + n2)) {
        if (pair_val[j] == nil) {
          dist_val[j] = (EdgeCost)0;
          q.push(j);
        }
      }
      dist_val[nil] = INFTY;

      while (!q.empty()) {
        int j = q.front();
        q.pop();
        if (j == nil) continue;
        for (auto it : g.adj[j]) {
          if (dist_val[pair_val[it.to]] == INFTY) {
            dist_val[pair_val[it.to]] = dist_val[j] + 1;
            q.push(pair_val[it.to]);
          }
        }
      }
      if (dist_val[nil] == INFTY) break;

      for (int j : range(n1 + n2)) if (pair_val[j] == nil && dfs(g, j)) res++;
    }
    return res;
  }
};

namespace solver {

template<typename T1, typename T2> struct In2 {
  T1 a; T2 b;
  friend std::istream& operator>>(std::istream& is, In2& obj) { T1 t1; T2 t2; is >> t1 >> t2; obj = {t1, t2}; return is; }
};

template<typename T1, typename T2, typename T3> struct In3 {
  T1 a; T2 b; T3 c;
  friend std::istream& operator>>(std::istream& is, In3& obj) { T1 t1; T2 t2; T3 t3; is >> t1 >> t2 >> t3; obj = {t1, t2, t3}; return is; }
};

template<typename T>
void vec_unique(vector<T>& v) {
  ranges::sort(v);
  auto result = ranges::unique(v);
  v.erase(result.begin(), result.end());
}

template<typename T>
ll vec_index(vector<T>& v, T val) {
  auto it = ranges::lower_bound(v, val);
  return it - v.begin();
}

int h, w;
vector<vector<int>> A;

void read() {
  cin >> h >> w;
  A.resize(h);
  for (int i : range(h)) take(A[i], w);
}

using RetType = int;

RetType run() {
  map<int, vector<pair<int, int>>> mp;
  for (int i : range(h)) 
  for (int j : range(w)) if (A[i][j]) mp[A[i][j]].push_back({i, j});

  int res = 0;
  for (auto it : mp) {
    auto& vp = it.second;
    vector<int> vi, vj;
    for (auto p : vp) vi.push_back(p.first), vj.push_back(p.second);
    vec_unique(vi);
    vec_unique(vj);

    int n1 = (int)vi.size(), n2 = (int)vj.size();
    G g(n1 + n2);

    for (auto p : vp) {
      int i1 = vec_index(vi, p.first);
      int j1 = vec_index(vj, p.second);
      g.add_undirected_edge(i1, n1 + j1);
    }
    BipartiteMatching bm;
    int m = bm.exec(g, n1, n2);

    res += m;
  }
  return res;
}

}  // namespace

template <typename F>
void run(F f) { if constexpr (std::is_same_v<decltype(f()), void>) f(); else cout << f() << endl; }

int main(int argc, char** argv) {
  cerr << fixed << setprecision(12);
  cout << fixed << setprecision(12);
  int testcase = 1;
  if (argc > 1) testcase = atoi(argv[1]);
  while (testcase--) {
    solver::read();
  }
  run(solver::run);
}