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

int main() {
    int H, W;
    std::cin >> H >> W;
    std::vector A(H, std::vector<int>(W));
    for (auto &r : A) for (int &a : r) std::cin >> a;

    std::vector<std::pair<int, int>> rows, cols;
    for (int i = 0; i < H; i++) {
        for (int j = 0; j < W; j++) {
            if (A[i][j] == 0) continue;
            rows.emplace_back(i, A[i][j]);
            cols.emplace_back(j, A[i][j]);
        }
    }

    std::sort(rows.begin(), rows.end());
    rows.erase(std::unique(rows.begin(), rows.end()), rows.end());
    std::sort(cols.begin(), cols.end());
    cols.erase(std::unique(cols.begin(), cols.end()), cols.end());

    int R = rows.size(), C = cols.size();
    atcoder::mf_graph<int> graph(R + C + 2);
    int source = R + C, sink = source + 1;
    for (int i = 0; i < R; i++) graph.add_edge(source, i, 1);
    for (int i = 0; i < C; i++) graph.add_edge(i + R, sink, 1);
    for (int i = 0; i < H; i++) {
        for (int j = 0; j < W; j++) {
            int r = std::lower_bound(rows.begin(), rows.end(), std::pair{i, A[i][j]}) - rows.begin();
            int c = std::lower_bound(cols.begin(), cols.end(), std::pair{j, A[i][j]}) - cols.begin();
            graph.add_edge(r, c + R, 1);
        }
    }
    std::cout << graph.flow(source, sink) << std::endl;
}