#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<numeric>
#include<cmath>
#include<utility>
#include<tuple>
#include<cstdint>
#include<cstdio>
#include<iomanip>
#include<map>
#include<queue>
#include<set>
#include<stack>
#include<deque>
#include<unordered_map>
#include<unordered_set>
#include<bitset>
#include<cctype>
#include<chrono>
#include<random>
#include<cassert>
#include<cstddef>
#include<iterator>
#include<string_view>
#include<type_traits>

#ifdef LOCAL
#  include "debug_print.hpp"
#  define debug(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define debug(...) (static_cast<void>(0))
#endif

using namespace std;
#define rep(i,n) for(int i=0; i<(n); i++)
#define rrep(i,n) for(int i=(n)-1; i>=0; i--)
#define FOR(i,a,b) for(int i=(a); i<(b); i++)
#define RFOR(i,a,b) for(int i=(b-1); i>=(a); i--)
#define ALL(v) v.begin(), v.end()
#define RALL(v) v.rbegin(), v.rend()
#define UNIQUE(v) v.erase( unique(v.begin(), v.end()), v.end() );
#define pb push_back
using ll = long long;
using D = double;
using LD = long double;
using P = pair<int, int>;
template<typename T> using PQ = priority_queue<T,vector<T>>;
template<typename T> using minPQ = priority_queue<T, vector<T>, greater<T>>;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
void yesno(bool flag) {cout << (flag?"Yes":"No") << "\n";}

template<typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
    os << p.first << " " << p.second;
    return os;
}
template<typename T, typename U>
istream &operator>>(istream &is, pair<T, U> &p) {
    is >> p.first >> p.second;
    return is;
}

template<typename T>
ostream &operator<<(ostream &os, const vector<T> &v) {
    int s = (int)v.size();
    for (int i = 0; i < s; i++) os << (i ? " " : "") << v[i];
    return os;
}
template<typename T>
istream &operator>>(istream &is, vector<T> &v) {
    for (auto &x : v) is >> x;
    return is;
}
void in() {}
template<typename T, class... U>
void in(T &t, U &...u) {
    cin >> t;
    in(u...);
}
void out() { cout << "\n"; }
template<typename T, class... U, char sep = ' '>
void out(const T &t, const U &...u) {
    cout << t;
    if (sizeof...(u)) cout << sep;
    out(u...);
}
void outr() {}
template<typename T, class... U, char sep = ' '>
void outr(const T &t, const U &...u) {
    cout << t;
    outr(u...);
}

#include "atcoder/maxflow.hpp"

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int h,w; in(h,w);
    int a[h][w];
    rep(i,h)rep(j,w) in(a[i][j]);
    vector<int> bin;
    rep(i,h)rep(j,w) {
        if(a[i][j] == 0) continue;
        bin.pb(a[i][j]);
    }
    sort(ALL(bin));
    UNIQUE(bin);
    rep(i,h)rep(j,w){
        if(a[i][j] == 0) continue;
        a[i][j] = lower_bound(ALL(bin), a[i][j]) - bin.begin() + 1;
    }
    int m = bin.size();
    vector<vector<P>> pos(m+1);
    rep(i,h)rep(j,w){
        pos[a[i][j]].pb({i,j});
    }
    ll ans = 0;
    FOR(i,1,m+1){
        if(pos[i].empty()) continue;
        set<int> mh, mw;
        for(auto &[x,y] : pos[i]){
            mh.insert(x);
            mw.insert(y);
        }
        int nh = mh.size(), nw = mw.size();
        vector<int> vx(nh),vy(nw);
        int now = 0;
        for(auto x : mh){
            vx[now] = x;
            now++;
        }
        now = 0;
        for(auto y : mw){
            vy[now] = y;
            now++;
        }
        map<int,int> mph,mpw;
        rep(i,nh) mph[vx[i]] = i;
        rep(i,nw) mpw[vy[i]] = i;
        int sz = nh+nw;
        atcoder::mf_graph<ll> g(2*sz+2);
        for(auto &[x,y] : pos[i]){
            int nx = mph[x];
            int ny = mpw[y];
            g.add_edge(nx,nh+ny,1);
        }
        rep(i,nh) g.add_edge(2*sz, i, 1);
        rep(i,nw) g.add_edge(i+nh, 2*sz+1, 1);
        ans += g.flow(2*sz ,2*sz+1);
    }
    out(ans);
}