/**
 *    author:  otera
 *    created: 16.04.2021 20:18:53 
**/
#include<bits/stdc++.h>
using namespace std;

using ll = long long;
using ld = long double;
using ull = unsigned long long;
using uint = unsigned;
const int inf=1e9+7;
const ll INF=1LL<<60;
#define repa(i, n) for(int i = 0; i < n; ++ i)
#define repb(i, a, b) for(int i = a; i < b; ++ i)
#define repc(i, a, b, c) for(int i = a; i < b; i += c)
#define overload4(a, b, c, d, e, ...) e
#define rep(...) overload4(__VA_ARGS__, repc, repb, repa)(__VA_ARGS__)
#define rep1a(i, n) for(int i = 0; i <= n; ++ i)
#define rep1b(i, a, b) for(int i = a; i <= b; ++ i)
#define rep1c(i, a, b, c) for(int i = a; i <= b; i += c)
#define rep1(...) overload4(__VA_ARGS__, rep1c, rep1b, rep1a)(__VA_ARGS__)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define per1(i,n) for(int i=n;i>=1;i--)
typedef pair<int, int> P;
typedef pair<ll, ll> LP;
#define pb push_back
#define eb emplace_back
#define fr first
#define sc second
#define all(c) c.begin(),c.end()
#define lb(c, x) distance((c).begin(), lower_bound(all(c), (x)))
#define ub(c, x) distance((c).begin(), upper_bound(all(c), (x)))
#define Sort(a) sort(all(a))
#define Rev(a) reverse(all(a))
#define Uniq(a) sort(all(a));a.erase(unique(all(a)),end(a))
#define si(c) (int)(c).size()
inline ll popcnt(ull a){ return __builtin_popcountll(a); }
#define tpow(n) (1LL<<(n))
#define unless(A) if(!(A))
ll intpow(ll a, ll b){ ll ans = 1; while(b){ if(b & 1) ans *= a; a *= a; b /= 2; } return ans; }
ll intpow(ll a, ll b, ll m) {ll ans = 1; while(b){ if(b & 1) (ans *= a) %= m; (a *= a) %= m; b /= 2; } return ans; }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
#define INT(...) int __VA_ARGS__;in(__VA_ARGS__)
#define LL(...) ll __VA_ARGS__;in(__VA_ARGS__)
#define ULL(...) ull __VA_ARGS__;in(__VA_ARGS__)
#define STR(...) string __VA_ARGS__;in(__VA_ARGS__)
#define CHR(...) char __VA_ARGS__;in(__VA_ARGS__)
#define DBL(...) double __VA_ARGS__;in(__VA_ARGS__)
#define LD(...) ld __VA_ARGS__;in(__VA_ARGS__)
#define vec(type,name,...) vector<type>name(__VA_ARGS__)
#define VEC(type,name,size) vector<type>name(size);in(name)
#define vv(type,name,h,...) vector<vector<type>>name(h,vector<type>(__VA_ARGS__))
#define VV(type,name,h,w) vector<vector<type>>name(h,vector<type>(w));in(name)
#define vvv(type,name,h,w,...) vector<vector<vector<type>>>name(h,vector<vector<type>>(w,vector<type>(__VA_ARGS__)))
template <class T> using vc = vector<T>;
template <class T> using vvc = vector<vc<T>>;
template <class T> using vvvc = vector<vvc<T>>;
template <class T> using vvvvc = vector<vvvc<T>>;
template <class T> using pq = priority_queue<T>;
template <class T> using pqg = priority_queue<T, vector<T>, greater<T>>;
template<class T> void scan(T& a){ cin >> a; }
template<class T> void scan(vector<T>& a){ for(auto&& i : a) scan(i); }
void in(){}
template <class Head, class... Tail> void in(Head& head, Tail&... tail){ scan(head); in(tail...); }
void print(){ cout << ' '; }
template<class T> void print(const T& a){ cout << a; }
template<class T> void print(const vector<T>& a){ if(a.empty()) return; print(a[0]); for(auto i = a.begin(); ++i != a.end(); ){ cout << ' '; print(*i); } }
int out(){ cout << '\n'; return 0; }
template<class T> int out(const T& t){ print(t); cout << '\n'; return 0; }
template<class Head, class... Tail> int out(const Head& head, const Tail&... tail){ print(head); cout << ' '; out(tail...); return 0; }
#define CHOOSE(a) CHOOSE2 a
#define CHOOSE2(a0,a1,a2,a3,a4,x,...) x
#define debug_1(x1) cout<<#x1<<": "<<x1<<endl
#define debug_2(x1,x2) cout<<#x1<<": "<<x1<<", "#x2<<": "<<x2<<endl
#define debug_3(x1,x2,x3) cout<<#x1<<": "<<x1<<", "#x2<<": "<<x2<<", "#x3<<": "<<x3<<endl
#define debug_4(x1,x2,x3,x4) cout<<#x1<<": "<<x1<<", "#x2<<": "<<x2<<", "#x3<<": "<<x3<<", "#x4<<": "<<x4<<endl
#define debug_5(x1,x2,x3,x4,x5) cout<<#x1<<": "<<x1<<", "#x2<<": "<<x2<<", "#x3<<": "<<x3<<", "#x4<<": "<<x4<<", "#x5<<": "<<x5<<endl
#ifdef DEBUG
#define debug(...) CHOOSE((__VA_ARGS__,debug_5,debug_4,debug_3,debug_2,debug_1,~))(__VA_ARGS__)
#define dump(...) { print(#__VA_ARGS__); print(":"); out(__VA_ARGS__); }
#else
#define debug(...)
#define dump(...)
#endif

// struct Bipartite_Matching
// {
//   vector< vector< int > > graph;
//   vector< int > dist, match;
//   vector< bool > used, vv;

//   Bipartite_Matching(int n, int m)
//   {
//     graph.resize(n);
//     match.assign(m, -1);
//     used.assign(n, false);
//   }

//   void add_edge(int u, int v)
//   {
//     graph[u].push_back(v);
//   }

//   void bfs()
//   {
//     dist.assign(graph.size(), -1);
//     queue< int > que;
//     for(int i = 0; i < graph.size(); i++) {
//       if(!used[i]) {
//         que.emplace(i);
//         dist[i] = 0;
//       }
//     }

//     while(!que.empty()) {
//       int a = que.front();
//       que.pop();
//       for(auto &b : graph[a]) {
//         int c = match[b];
//         if(c >= 0 && dist[c] == -1) {
//           dist[c] = dist[a] + 1;
//           que.emplace(c);
//         }
//       }
//     }
//   }

//   bool dfs(int a)
//   {
//     vv[a] = true;
//     for(auto &b : graph[a]) {
//       int c = match[b];
//       if(c < 0 || (!vv[c] && dist[c] == dist[a] + 1 && dfs(c))) {
//         match[b] = a;
//         used[a] = true;
//         return (true);
//       }
//     }
//     return (false);
//   }

//   int bipartite_matching()
//   {
//     int ret = 0;
//     while(true) {
//       bfs();
//       vv.assign(graph.size(), false);
//       int flow = 0;
//       for(int i = 0; i < graph.size(); i++) {
//         if(!used[i] && dfs(i)) ++flow;
//       }
//       if(flow == 0) return (ret);
//       ret += flow;
//     }
//   }
// };

struct Bipartite_Matching
{
  vector< vector< int > > graph;
  vector< int > match, alive, used;
  int timestamp;
 
  Bipartite_Matching(int n)
  {
    timestamp = 0;
    graph.resize(n);
    alive.assign(n, 1);
    used.assign(n, 0);
    match.assign(n, -1);
  }
 
  void add_edge(int u, int v)
  {
    graph[u].push_back(v);
    graph[v].push_back(u);
  }
 
  bool dfs(int v)
  {
    used[v] = timestamp;
    for(int i = 0; i < graph[v].size(); i++) {
      int u = graph[v][i], w = match[u];
      if(alive[u] == 0) continue;
      if(w == -1 || (used[w] != timestamp && dfs(w))) {
        match[v] = u;
        match[u] = v;
        return (true);
      }
    }
    return (false);
  }
 
  int bipartite_matching()
  {
    int ret = 0;
    for(int i = 0; i < graph.size(); i++) {
      if(alive[i] == 0) continue;
      if(match[i] == -1) {
        ++timestamp;
        ret += dfs(i);
      }
    }
    return (ret);
  } 
};

const int MAX = 500500;

void solve() {
    INT(h, w);
    VV(int, a, h, w);
    int ans = 0;
    vvc<int> g(MAX);
    rep(i, h) {
        rep(j, w) {
            g[a[i][j]].eb(i * w + j);
        }
    }
    for(int x = MAX - 1; x > 0; -- x) {
        if(si(g[x]) == 0) continue;
        vc<int> p, q;
        for(int y: g[x]) {
            int i = y / w, j = y % w;
            p.eb(i), q.eb(j);
        }
        Uniq(p), Uniq(q);
        int n = si(p) + si(q);
        int m = si(g[x]);
        Bipartite_Matching bm(n);
        for(int y: g[x]) {
            int i = y / w, j = y % w;
            debug(x, i, j);
            bm.add_edge(lb(p, i), lb(q, j) + si(p));
            // bm.add_edge(lb(q, j) + si(p), lb(p, i));
        }
        int cost = bm.bipartite_matching();
        debug(x, cost);
        ans += cost;
    }
    out(ans);
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    // cout << fixed << setprecision(20);
    // INT(t); rep(i, t)solve();
    solve();
    return 0;
}