#include <bits/stdc++.h>
using namespace std;
#ifdef tabr
#include "library/debug.cpp"
#else
#define debug(...)
#endif

struct matching {
    vector<vector<int>> g;
    vector<int> pa;
    vector<int> pb;
    vector<int> was;
    int n, m;
    int res;
    int iter;

    matching(int _n, int _m) : n(_n), m(_m) {
        pa.assign(n, -1);
        pb.assign(m, -1);
        was.resize(n);
        g.resize(n);
        res = 0;
        iter = 0;
    }

    void add(int from, int to) {
        g[from].push_back(to);
    }

    bool dfs(int v) {
        was[v] = iter;
        for (int u : g[v]) {
            if (pb[u] == -1) {
                pa[v] = u;
                pb[u] = v;
                return true;
            }
        }
        for (int u : g[v]) {
            if (was[pb[u]] != iter && dfs(pb[u])) {
                pa[v] = u;
                pb[u] = v;
                return true;
            }
        }
        return false;
    }

    int solve() {
        while (true) {
            iter++;
            int add = 0;
            for (int i = 0; i < n; i++) {
                if (pa[i] == -1 && dfs(i)) {
                    add++;
                }
            }
            if (add == 0) {
                break;
            }
            res += add;
        }
        return res;
    }
};

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int h, w;
    cin >> h >> w;
    vector<vector<int>> a(h, vector<int>(w));
    int m = 500001;
    vector<vector<pair<int, int>>> b(m);
    for (int i = 0; i < h; i++) {
        for (int j = 0; j < w; j++) {
            cin >> a[i][j];
            b[a[i][j]].emplace_back(i, j);
        }
    }
    int ans = 0;
    for (int i = m - 1; i > 0; i--) {
        if (b[i].empty()) {
            continue;
        }
        vector<int> s, t;
        for (auto [x, y] : b[i]) {
            s.emplace_back(x);
            t.emplace_back(y);
        }
        sort(s.begin(), s.end());
        s.resize(unique(s.begin(), s.end()) - s.begin());
        sort(t.begin(), t.end());
        t.resize(unique(t.begin(), t.end()) - t.begin());
        matching mt((int)s.size(), (int)t.size());
        for (auto [x, y] : b[i]) {
            int from = (int)(lower_bound(s.begin(), s.end(), x) - s.begin());
            int to = (int)(lower_bound(t.begin(), t.end(), y) - t.begin());
            mt.add(from, to);
        }
        ans += mt.solve();
    }
    cout << ans << '\n';
    return 0;
}