#include <atcoder/maxflow>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
const long long INF_LL = 2000000000000000000LL;
const int INF = 2000000000;
const long long MOD = 1000000007;
#define ll long long
#define all(x) x.begin(), x.end()
#define REP(i, a, b) for(int i = a; i < b; i++)
#define rep(i, n) REP(i, 0, n)
// typedef float double;
// typedef priority_queue prique;
typedef pair<ll, ll> P;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<P> vp;
typedef vector<ll> vl;
typedef vector<vi> matrix;
int dx[4] = {0, -1, 0, 1};
int dy[4] = {1, 0, -1, 0};
int sign[2] = {1, -1};
template <class T> bool chmax(T &a, T b) {
    if(a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T> bool chmin(T &a, T b) {
    if(a > b) {
        a = b;
        return 1;
    }
    return 0;
}

ll modpow(ll a, ll b, ll m) {
    if(b == 0)
        return 1;
    ll t = modpow(a, b / 2, m);
    if(b & 1) {
        return (t * t % m) * a % m;
    } else {
        return t * t % m;
    }
}

struct edge {
    int to;
    ll cost;
    edge(int t, ll c) { to = t, cost = c; }
};

typedef vector<vector<edge>> graph;

// using mint = modint998244353;

int main(){
    int h, w;
    cin >> h >> w;
    vector<vector<int>> a(h, vector<int>(w));
    rep(i, h) rep(j, w) cin >> a[i][j];
    vector<vector<pair<int, int>>> t(500000);
    rep(i, h){
        rep(j, w){
            if(a[i][j] > 0) t[a[i][j] - 1].push_back({i, j});
        }
    }
    mf_graph<int> g(h + w + 2);
    rep(i, h) g.add_edge(h + w, i, 1);
    rep(i, w) g.add_edge(i + h, h + w + 1, 1);
    int idx = h + w;
    int ans = 0;
    for(int i = 499999; i >= 0; i--){
        rep(j, t[i].size()){
            g.add_edge(t[i][j].first, t[i][j].second + h, 1);
        }
        if(t[i].size() > 0) {
            ans += g.flow(h + w, h + w + 1);
            g.flow(h + w + 1, h + w);
            REP(j, idx, idx + t[i].size()){
                g.change_edge(j, 0, 0);
            }
        }
        idx += t[i].size();
    }
    cout << ans << endl;
}