#include <bits/stdc++.h>
#include <atcoder/maxflow>

using namespace std;
using namespace atcoder;

int main()
{
    int h, w;
    cin >> h >> w;
    vector a(h, vector<int>(w));
    for (int i = 0; i < h; i++)
    {
        for (int j = 0; j < w; j++)
        {
            cin >> a.at(i).at(j);
        }
    }
    unordered_map<int, vector<pair<int, int>>> m;
    for (int i = 0; i < h; i++)
    {
        for (int j = 0; j < w; j++)
        {
            if (a.at(i).at(j))
            {
                m[a.at(i).at(j)].emplace_back(i, h + j);
            }
        }
    }
    int ans = 0;
    for (auto &&[i, v] : m)
    {
        unordered_map<int, int> newindex;
        for (auto &&k : v)
        {
            if (newindex[k.first] == 0)
            {
                newindex[k.first] = newindex.size();
            }
            if (newindex[k.second] == 0)
            {
                newindex[k.second] = newindex.size();
            }
        }
        const int n = newindex.size();
        int s = 0, t = n + 1;
        mf_graph<int> flow(n + 2);
        vector<bool> used(n + 2);
        for (auto &&k : v)
        {
            flow.add_edge(newindex[k.first], newindex[k.second], 1);
            if (not used.at(newindex[k.first]))
            {
                flow.add_edge(s, newindex[k.first], 1);
                used.at(newindex[k.first]) = true;
            }
            if (not used.at(newindex[k.second]))
            {
                flow.add_edge(newindex[k.second], t, 1);
                used.at(newindex[k.second]) = true;
            }
        }
        ans += flow.flow(s, t);
    }
    cout << ans << endl;
    return 0;
}