#define LOCAL
#include <bits/stdc++.h>
using namespace std;
#pragma region Macros
typedef long long ll;
typedef __int128_t i128;
typedef unsigned int uint;
typedef unsigned long long ull;
#define ALL(x) (x).begin(), (x).end()

template <typename T> istream& operator>>(istream& is, vector<T>& v) {
    for (T& x : v) is >> x;
    return is;
}
template <typename T> ostream& operator<<(ostream& os, const vector<T>& v) {
    for (int i = 0; i < (int)v.size(); i++) {
        os << v[i] << (i + 1 == (int)v.size() ? "" : " ");
    }
    return os;
}
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, typename V> ostream& operator<<(ostream& os, const tuple<T, U, V>& t) {
    os << '(' << get<0>(t) << ',' << get<1>(t) << ',' << get<2>(t) << ')';
    return os;
}
template <typename T, typename U, typename V, typename W> ostream& operator<<(ostream& os, const tuple<T, U, V, W>& t) {
    os << '(' << get<0>(t) << ',' << get<1>(t) << ',' << get<2>(t) << ',' << get<3>(t) << ')';
    return os;
}
template <typename T, typename U> ostream& operator<<(ostream& os, const map<T, U>& m) {
    os << '{';
    for (auto itr = m.begin(); itr != m.end();) {
        os << '(' << itr->first << ',' << itr->second << ')';
        if (++itr != m.end()) os << ',';
    }
    os << '}';
    return os;
}
template <typename T, typename U> ostream& operator<<(ostream& os, const unordered_map<T, U>& m) {
    os << '{';
    for (auto itr = m.begin(); itr != m.end();) {
        os << '(' << itr->first << ',' << itr->second << ')';
        if (++itr != m.end()) os << ',';
    }
    os << '}';
    return os;
}
template <typename T> ostream& operator<<(ostream& os, const set<T>& s) {
    os << '{';
    for (auto itr = s.begin(); itr != s.end();) {
        os << *itr;
        if (++itr != s.end()) os << ',';
    }
    os << '}';
    return os;
}
template <typename T> ostream& operator<<(ostream& os, const multiset<T>& s) {
    os << '{';
    for (auto itr = s.begin(); itr != s.end();) {
        os << *itr;
        if (++itr != s.end()) os << ',';
    }
    os << '}';
    return os;
}
template <typename T> ostream& operator<<(ostream& os, const unordered_set<T>& s) {
    os << '{';
    for (auto itr = s.begin(); itr != s.end();) {
        os << *itr;
        if (++itr != s.end()) os << ',';
    }
    os << '}';
    return os;
}
template <typename T> ostream& operator<<(ostream& os, const deque<T>& v) {
    for (int i = 0; i < (int)v.size(); i++) {
        os << v[i] << (i + 1 == (int)v.size() ? "" : " ");
    }
    return os;
}

void debug_out() { cerr << '\n'; }
template <class Head, class... Tail> void debug_out(Head&& head, Tail&&... tail) {
    cerr << head;
    if (sizeof...(Tail) > 0) cerr << ", ";
    debug_out(move(tail)...);
}
#ifdef LOCAL
#define debug(...)                                                                   \
    cerr << " ";                                                                     \
    cerr << #__VA_ARGS__ << " :[" << __LINE__ << ":" << __FUNCTION__ << "]" << '\n'; \
    cerr << " ";                                                                     \
    debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

template <typename T> T gcd(T x, T y) { return y != 0 ? gcd(y, x % y) : x; }
template <typename T> T lcm(T x, T y) { return x / gcd(x, y) * y; }

template <class T1, class T2> inline bool chmin(T1& a, T2 b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <class T1, class T2> inline bool chmax(T1& a, T2 b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
#pragma endregion

/**
 * @brief compress
 */
template <typename T> map<T, int> compress(vector<T>& v) {
    sort(v.begin(), v.end());
    v.erase(unique(v.begin(), v.end()), v.end());
    map<T, int> res;
    for (int i = 0; i < v.size(); i++) res[v[i]] = i;
    return res;
}

/**
 * @brief Hopcroft Karp
 * @docs docs/flow/HopcroftKarp.md
 */
struct HopcroftKarp {
private:
    int n, m;
    bool matched;
    vector<vector<int>> G, rG;
    vector<int> match_l, match_r, level;
    void levelize() {
        queue<int> que;
        for (int i = 0; i < n; i++) {
            level[i] = -1;
            if (match_l[i] < 0) {
                level[i] = 0;
                que.emplace(i);
            }
        }
        while (!que.empty()) {
            int v = que.front();
            que.pop();
            for (int u : G[v]) {
                int w = match_r[u];
                if (~w && level[w] < 0) {
                    level[w] = level[v] + 1;
                    que.emplace(w);
                }
            }
        }
    }
    bool find_augumenting_path(int v) {
        for (int u : G[v]) {
            int w = match_r[u];
            if (w < 0 || (level[w] > level[v] && find_augumenting_path(w))) {
                match_l[v] = u;
                match_r[u] = v;
                return true;
            }
        }
        return false;
    }
    vector<vector<int>> build_residual_graph() {
        if (!matched) max_matching();
        const int s = n + m, t = n + m + 1;
        vector<vector<int>> res(n + m + 2);
        for (int i = 0; i < n; i++) {
            if (match_l[i] < 0) {
                res[s].emplace_back(i);
            }
        }
        for (int i = 0; i < n; i++) {
            for (int j : G[i]) {
                if (match_l[i] == j)
                    res[j + n].emplace_back(i);
                else
                    res[i].emplace_back(j + n);
            }
        }
        return res;
    }
    vector<bool> find_residual_path() {
        auto g = build_residual_graph();
        queue<int> que;
        vector<bool> visited(n + m + 2);
        que.emplace(n + m);
        visited[n + m] = true;
        while (!que.empty()) {
            int v = que.front();
            que.pop();
            for (int u : g[v]) {
                if (visited[u]) continue;
                visited[u] = true;
                que.emplace(u);
            }
        }
        return visited;
    }

public:
    HopcroftKarp(int n, int m) : n(n), m(m), G(n), rG(m), match_l(n, -1), match_r(m, -1), level(n), matched(false) {}
    void add_edge(int u, int v) {
        G[u].emplace_back(v);
        rG[v].emplace_back(u);
    }
    vector<pair<int, int>> max_matching() {
        matched = true;
        while (1) {
            levelize();
            int match = 0;
            for (int i = 0; i < n; i++) {
                if (match_l[i] < 0) {
                    match += find_augumenting_path(i);
                }
            }
            if (!match) break;
        }
        vector<pair<int, int>> res;
        for (int i = 0; i < n; i++) {
            if (~match_l[i]) {
                res.emplace_back(i, match_l[i]);
            }
        }
        return res;
    }
    vector<int> min_vertex_cover() {
        auto visited = find_residual_path();
        vector<int> res;
        for (int i = 0; i < n + m; i++) {
            if (visited[i] ^ (i < n)) {
                res.emplace_back(i);
            }
        }
        return res;
    }
    vector<int> max_independent_set() {
        auto visited = find_residual_path();
        vector<int> res;
        for (int i = 0; i < n + m; i++) {
            if (visited[i] ^ (i >= n)) {
                res.emplace_back(i);
            }
        }
        return res;
    }
    vector<pair<int, int>> min_edge_cover() {
        auto res = max_matching();
        for (int i = 0; i < n; i++) {
            if (~match_l[i]) continue;
            if (G[i].empty()) return {};
            res.emplace_back(i, G[i][0]);
        }
        for (int i = 0; i < m; i++) {
            if (~match_r[i]) continue;
            if (rG[i].empty()) return {};
            res.emplace_back(rG[i][0], i);
        }
        return res;
    }
};

const int INF = 1e9;
const long long IINF = 1e18;
const int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const char dir[4] = {'D', 'R', 'U', 'L'};
const long long MOD = 1000000007;
// const long long MOD = 998244353;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int H, W;
    cin >> H >> W;
    vector<vector<int>> A(H, vector<int>(W));
    cin >> A;

    vector<int> comp;
    for (int i = 0; i < H; i++) {
        for (int j = 0; j < W; j++) {
            if (A[i][j] == 0) continue;
            comp.emplace_back(A[i][j]);
        }
    }
    map<int, int> mp = compress(comp);
    int sz = mp.size();
    vector<vector<pair<int, int>>> es(sz);
    for (int i = 0; i < H; i++) {
        for (int j = 0; j < W; j++) {
            if (A[i][j] == 0) continue;
            es[mp[A[i][j]]].emplace_back(i, j);
        }
    }

    int ans = 0;
    for (auto& v : es) {
        vector<int> h, w;
        for (auto& p : v) {
            h.emplace_back(p.first);
            w.emplace_back(p.second);
        }
        map<int, int> mh = compress(h), mw = compress(w);
        int x = mh.size(), y = mw.size();
        HopcroftKarp HK(x, y);
        for (auto& p : v) HK.add_edge(mh[p.first], mw[p.second]);
        ans += HK.max_matching().size();
    }

    cout << ans << '\n';
    return 0;
}