#include <atcoder/maxflow>
#include <iostream>
#include <vector>
#include <set>

using namespace std;
constexpr int X = 500000;

void solve() {
    int h, w;
    cin >> h >> w;

    vector<vector<pair<int, int>>> ess(X);
    for (int i = 0; i < h; ++i) {
        for (int j = 0; j < w; ++j) {
            int x;
            cin >> x;
            if (x > 0) ess[--x].emplace_back(i, j);
        }
    }

    int ans = 0;
    for (const auto& es : ess) {
        if (es.empty()) continue;

        atcoder::mf_graph<int> graph(h + w + 2);
        int s = h + w, g = s + 1;

        set<int> is, js;
        for (auto [i, j] : es) {
            is.insert(i);
            js.insert(j);
            graph.add_edge(i, h + j, 1);
        }

        for (auto i : is) graph.add_edge(s, i, 1);
        for (auto j : js) graph.add_edge(h + j, g, 1);
        ans += graph.flow(s, g);
    }

    cout << ans << "\n";
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    solve();

    return 0;
}