#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define pb(x) push_back(x)
#define mp(a, b) make_pair(a, b)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define lscan(x) scanf("%I64d", &x)
#define lprint(x) printf("%I64d", x)
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define rep2(i, n) for (ll i = n - 1; i >= 0; i--)
#define REP(i, l, r) for (ll i = l; i < (r); i++)
template <class T>
using rque = priority_queue<T, vector<T>, greater<T>>;
const ll mod = 998244353;

template <class T>
bool chmin(T &a, const T &b) {
    if (b < a) {
        a = b;
        return 1;
    }
    return 0;
}

template <class T>
bool chmax(T &a, const T &b) {
    if (b > a) {
        a = b;
        return 1;
    }
    return 0;
}

ll gcd(ll a, ll b)
{
	ll c = a % b;
	while (c != 0)
	{
		a = b;
		b = c;
		c = a % b;
	}
	return b;
}

long long extGCD(long long a, long long b, long long &x, long long &y)
{
	if (b == 0)
	{
		x = 1;
		y = 0;
		return a;
	}
	long long d = extGCD(b, a % b, y, x);
	y -= a / b * x;
	return d;
}

struct UnionFind
{
	vector<ll> data;

	UnionFind(int sz)
	{
		data.assign(sz, -1);
	}

	bool unite(int x, int y)
	{
		x = find(x), y = find(y);
		if (x == y)
			return (false);
		if (data[x] > data[y])
			swap(x, y);
		data[x] += data[y];
		data[y] = x;
		return (true);
	}

	int find(int k)
	{
		if (data[k] < 0)
			return (k);
		return (data[k] = find(data[k]));
	}

	ll size(int k)
	{
		return (-data[find(k)]);
	}
};

ll M = 1000000007;

vector<ll> fac(2000011, 0);  //n!(mod M)
vector<ll> ifac(2000011); //k!^{M-2} (mod M)

ll mpow(ll x, ll n)
{
	ll ans = 1;
	while (n != 0)
	{
		if (n & 1)
			ans = ans * x % M;
		x = x * x % M;
		n = n >> 1;
	}
	return ans;
}
ll mpow2(ll x, ll n, ll mod)
{
	ll ans = 1;
	while (n != 0)
	{
		if (n & 1)
			ans = ans * x % mod;
		x = x * x % mod;
		n = n >> 1;
	}
	return ans;
}
void setcomb()
{
	fac[0] = 1;
	ifac[0] = 1;
	for (ll i = 0; i < 2000010; i++)
	{
		fac[i + 1] = fac[i] * (i + 1) % M; // n!(mod M)
	}
	ifac[2000010] = mpow(fac[2000010], M - 2);
	for (ll i = 2000010; i > 0; i--)
	{
		ifac[i - 1] = ifac[i] * i % M;
	}
}
ll comb(ll a, ll b)
{
	if(fac[0] == 0)
		setcomb();
	if (a == 0 && b == 0)
		return 1;
	if (a < b || a < 0)
		return 0;
	ll tmp = ifac[a - b] * ifac[b] % M;
	return tmp * fac[a] % M;
}
ll perm(ll a, ll b)
{
	if (a == 0 && b == 0)
		return 1;
	if (a < b || a < 0)
		return 0;
	return fac[a] * ifac[a - b] % M;
}
long long modinv(long long a)
{
	long long b = M, u = 1, v = 0;
	while (b)
	{
		long long t = a / b;
		a -= t * b;
		swap(a, b);
		u -= t * v;
		swap(u, v);
	}
	u %= M;
	if (u < 0)
		u += M;
	return u;
}
ll modinv2(ll a, ll mod)
{
	ll b = mod, u = 1, v = 0;
	while (b)
	{
		ll t = a / b;
		a -= t * b;
		swap(a, b);
		u -= t * v;
		swap(u, v);
	}
	u %= mod;
	if (u < 0)
		u += mod;
	return u;
}

template <int mod>
struct ModInt
{
	int x;

	ModInt() : x(0) {}

	ModInt(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}

	ModInt &operator+=(const ModInt &p)
	{
		if ((x += p.x) >= mod)
			x -= mod;
		return *this;
	}

	ModInt &operator-=(const ModInt &p)
	{
		if ((x += mod - p.x) >= mod)
			x -= mod;
		return *this;
	}

	ModInt &operator*=(const ModInt &p)
	{
		x = (int)(1LL * x * p.x % mod);
		return *this;
	}

	ModInt &operator/=(const ModInt &p)
	{
		*this *= p.inverse();
		return *this;
	}

	ModInt operator-() const { return ModInt(-x); }

	ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }

	ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }

	ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }

	ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }

	bool operator==(const ModInt &p) const { return x == p.x; }

	bool operator!=(const ModInt &p) const { return x != p.x; }

	ModInt inverse() const
	{
		int a = x, b = mod, u = 1, v = 0, t;
		while (b > 0)
		{
			t = a / b;
			swap(a -= t * b, b);
			swap(u -= t * v, v);
		}
		return ModInt(u);
	}

	ModInt pow(int64_t n) const
	{
		ModInt ret(1), mul(x);
		while (n > 0)
		{
			if (n & 1)
				ret *= mul;
			mul *= mul;
			n >>= 1;
		}
		return ret;
	}

	friend ostream &operator<<(ostream &os, const ModInt &p)
	{
		return os << p.x;
	}

	friend istream &operator>>(istream &is, ModInt &a)
	{
		int64_t t;
		is >> t;
		a = ModInt<mod>(t);
		return (is);
	}

	static int get_mod() { return mod; }
};

using mint = ModInt<mod>;

typedef vector<vector<mint>> Matrix;

Matrix mul(Matrix a, Matrix b)
{
	assert(a[0].size() == b.size());
	int i, j, k;
	int n = a.size(), m = b[0].size(), l = a[0].size();
	Matrix c(n, vector<mint>(m));
	for (i = 0; i < n; i++)
		for (k = 0; k < l; k++)
			for (j = 0; j < m; j++)
				c[i][j] += a[i][k] * b[k][j];
	return c;
}

Matrix mat_pow(Matrix x, ll n)
{
	ll k = x.size();
	Matrix ans(k, vector<mint>(k, 0));
	for (int i = 0; i < k; i++)
		ans[i][i] = 1;
	while (n != 0)
	{
		if (n & 1)
			ans = mul(ans, x);
		x = mul(x, x);
		n = n >> 1;
	}
	return ans;
}

template< typename flow_t >
struct Dinic {
  const flow_t INF;

  struct edge {
    int to;
    flow_t cap;
    int rev;
    bool isrev;
    int idx;
  };

  vector< vector< edge > > graph;
  vector< int > min_cost, iter;

  Dinic(int V) : INF(numeric_limits< flow_t >::max()), graph(V) {}

  void add_edge(int from, int to, flow_t cap, int idx = -1) {
    graph[from].emplace_back((edge) {to, cap, (int) graph[to].size(), false, idx});
    graph[to].emplace_back((edge) {from, 0, (int) graph[from].size() - 1, true, idx});
  }

  bool bfs(int s, int t) {
    min_cost.assign(graph.size(), -1);
    queue< int > que;
    min_cost[s] = 0;
    que.push(s);
    while(!que.empty() && min_cost[t] == -1) {
      int p = que.front();
      que.pop();
      for(auto &e : graph[p]) {
        if(e.cap > 0 && min_cost[e.to] == -1) {
          min_cost[e.to] = min_cost[p] + 1;
          que.push(e.to);
        }
      }
    }
    return min_cost[t] != -1;
  }

  flow_t dfs(int idx, const int t, flow_t flow) {
    if(idx == t) return flow;
    for(int &i = iter[idx]; i < graph[idx].size(); i++) {
      edge &e = graph[idx][i];
      if(e.cap > 0 && min_cost[idx] < min_cost[e.to]) {
        flow_t d = dfs(e.to, t, min(flow, e.cap));
        if(d > 0) {
          e.cap -= d;
          graph[e.to][e.rev].cap += d;
          return d;
        }
      }
    }
    return 0;
  }

  flow_t max_flow(int s, int t) {
    flow_t flow = 0;
    while(bfs(s, t)) {
      iter.assign(graph.size(), 0);
      flow_t f = 0;
      while((f = dfs(s, t, INF)) > 0) flow += f;
    }
    return flow;
  }

  vector<pair<pair<int,int>,int>> get_edges() {
      vector<pair<pair<int,int>,int>> E;
      for (int i = 0; i < graph.size(); i++)
      {
          for (auto &e : graph[i])
          {
              if (e.isrev)
                  continue;
              auto &rev_e = graph[e.to][e.rev];
              E.push_back(mp(mp(i, e.to), rev_e.cap));
          }
      }
      return E;
  }
  
  void output()
    {
        for (int i = 0; i < graph.size(); i++)
        {
            for (auto &e : graph[i])
            {
                if (e.isrev)
                    continue;
                auto &rev_e = graph[e.to][e.rev];
                cout << i << "->" << e.to << " (flow: " << rev_e.cap << "/" << rev_e.cap + e.cap << ")" << endl;
            }
        }
    }
};

int main(){
	ll h, w;
	cin >> h >> w;
	ll a;
	vector<pair<ll, ll>> li[500001];
	rep(i, h) rep(j, w) cin >> a, li[a].pb(mp(i, j));
	ll ans = 0;
	REP(i,1,500001){
		if(li[i].size() == 0)
			continue;
		vector<ll> veci, vecj;
		rep(j, li[i].size()) veci.pb(li[i][j].first), vecj.pb(li[i][j].second);
		sort(all(veci)), sort(all(vecj));
		map<ll, ll> mi, mj;
		ll pi = 0, pj = 0;
		rep(j,li[i].size()){
			if(j == 0){
				mi[veci[j]] = pi++;
				mj[vecj[j]] = pj++;
			}
			else{
				if(veci[j] != veci[j-1])
					mi[veci[j]] = pi++;
				if(vecj[j] != vecj[j-1])
					mj[vecj[j]] = pj++;
			}
		}
		rep(j, li[i].size()) li[i][j].first = mi[li[i][j].first], li[i][j].second = mj[li[i][j].second];
		Dinic<ll> mf(pi + pj + 2);
		rep(j, pi) mf.add_edge(pi + pj, j, 1);
		rep(j, pj) mf.add_edge(pi + j, pi + pj + 1, 1);
		rep(j, li[i].size()) mf.add_edge(li[i][j].first, pi + li[i][j].second, 1);
		ans += mf.max_flow(pi + pj, pi + pj + 1);
	}
	cout << ans << endl;
}