#line 2 "cpplib/util/template.hpp"
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("avx2")
#include<bits/stdc++.h>
using namespace std;
struct __INIT__{__INIT__(){cin.tie(0);ios::sync_with_stdio(false);cout<<fixed<<setprecision(15);}}__INIT__;
typedef long long lint;
#define INF (1LL<<60)
#define IINF (1<<30)
#define EPS (1e-10)
#define endl ('\n')
typedef vector<lint> vec;
typedef vector<vector<lint>> mat;
typedef vector<vector<vector<lint>>> mat3;
typedef vector<string> svec;
typedef vector<vector<string>> smat;
template<typename T>using V=vector<T>;
template<typename T>using VV=V<V<T>>;
template<typename T>inline void output(T t){bool f=0;for(auto i:t){cout<<(f?" ":"")<<i;f=1;}cout<<endl;}
template<typename T>inline void output2(T t){for(auto i:t)output(i);}
template<typename T>inline void debug(T t){bool f=0;for(auto i:t){cerr<<(f?" ":"")<<i;f=1;}cerr<<endl;}
template<typename T>inline void debug2(T t){for(auto i:t)debug(i);}
#define loop(n) for(long long _=0;_<(long long)(n);++_)
#define _overload4(_1,_2,_3,_4,name,...) name
#define __rep(i,a) repi(i,0,a,1)
#define _rep(i,a,b) repi(i,a,b,1)
#define repi(i,a,b,c) for(long long i=(long long)(a);i<(long long)(b);i+=c)
#define rep(...) _overload4(__VA_ARGS__,repi,_rep,__rep)(__VA_ARGS__)
#define _overload3_rev(_1,_2,_3,name,...) name
#define _rep_rev(i,a) repi_rev(i,0,a)
#define repi_rev(i,a,b) for(long long i=(long long)(b)-1;i>=(long long)(a);--i)
#define rrep(...) _overload3_rev(__VA_ARGS__,repi_rev,_rep_rev)(__VA_ARGS__)

// #define rep(i,...) for(auto i:range(__VA_ARGS__)) 
// #define rrep(i,...) for(auto i:reversed(range(__VA_ARGS__)))
// #define repi(i,a,b) for(lint i=lint(a);i<(lint)(b);++i)
// #define rrepi(i,a,b) for(lint i=lint(b)-1;i>=lint(a);--i)
// #define irep(i) for(lint i=0;;++i)
// inline vector<long long> range(long long n){if(n<=0)return vector<long long>();vector<long long>v(n);iota(v.begin(),v.end(),0LL);return v;}
// inline vector<long long> range(long long a,long long b){if(b<=a)return vector<long long>();vector<long long>v(b-a);iota(v.begin(),v.end(),a);return v;}
// inline vector<long long> range(long long a,long long b,long long c){if((b-a+c-1)/c<=0)return vector<long long>();vector<long long>v((b-a+c-1)/c);for(int i=0;i<(int)v.size();++i)v[i]=i?v[i-1]+c:a;return v;}
// template<typename T>inline T reversed(T v){reverse(v.begin(),v.end());return v;}
#define all(n) begin(n),end(n)
template<typename T,typename E>bool chmin(T& s,const E& t){bool res=s>t;s=min<T>(s,t);return res;}
template<typename T,typename E>bool chmax(T& s,const E& t){bool res=s<t;s=max<T>(s,t);return res;}
const vector<lint> dx={1,0,-1,0,1,1,-1,-1};
const vector<lint> dy={0,1,0,-1,1,-1,1,-1};
#define SUM(v) accumulate(all(v),0LL)
template<typename T,typename ...Args>auto make_vector(T x,int arg,Args ...args){if constexpr(sizeof...(args)==0)return vector<T>(arg,x);else return vector(arg,make_vector<T>(x,args...));}
#define extrep(v,...) for(auto v:__MAKE_MAT__({__VA_ARGS__}))
#define bit(n,a) ((n>>a)&1)
vector<vector<long long>> __MAKE_MAT__(vector<long long> v){if(v.empty())return vector<vector<long long>>(1,vector<long long>());long long n=v.back();v.pop_back();vector<vector<long long>> ret;vector<vector<long long>> tmp=__MAKE_MAT__(v);for(auto e:tmp)for(long long i=0;i<n;++i){ret.push_back(e);ret.back().push_back(i);}return ret;}
using graph=vector<vector<int>>;
template<typename T>using graph_w=vector<vector<pair<int,T>>>;
template<typename T,typename E>ostream& operator<<(ostream& out,pair<T,E>v){out<<"("<<v.first<<","<<v.second<<")";return out;}
constexpr inline long long powll(long long a,long long b){long long res=1;while(b--)res*=a;return res;}
#line 10 "cpplib/graph_tree/dinic.hpp"

/**
 * @brief 最大流(Dinic法)
 */

template<typename T>
struct dinic {
    struct edge {
        int to;
        typename std::list<edge>::iterator rev;
        T cap,flow;
        edge(int to,T cap):to(to),cap(cap),flow(T()){}
    };
    int n,src,dst;
    T ret=T();
    std::vector<std::list<edge>> g;
    std::vector<typename std::list<edge>::iterator>itr;
    std::vector<int>level,seen;
    std::map<std::pair<int,int>,bool>exist;
    std::map<std::pair<int,int>,typename std::list<edge>::iterator>m;
    dinic(){}
    dinic(int n,int s,int t):n(n),src(s),dst(t){g.assign(n,std::list<edge>());itr.resize(n);}

    void add_edge(int from, int to, T cap) {
        g[from].push_back(edge(to,cap));
        g[to].push_back(edge(from,0));
        m[std::make_pair(from,to)]=prev(g[from].end());
        m[std::make_pair(to,from)]=prev(g[to].end());
        g[from].back().rev=prev(g[to].end());
        g[to].back().rev=prev(g[from].end());
        exist[std::make_pair(from,to)]=1;
        exist[std::make_pair(to,from)]=1;
    }
    bool update_edge(int from, int to, T cap){
        if(cap>0){
            if(exist[std::make_pair(from,to)]){
                auto e=m[std::make_pair(from,to)];
                e->cap+=cap;
            }else{
                add_edge(from,to,cap);
            }
            return 1;
        }else{
            cap*=-1;
            if(exist[std::make_pair(from,to)]){
                auto e=m[std::make_pair(from,to)];
                if(e->cap-e->flow>=cap){
                    e->cap-=cap;
                }else{
                    e->cap-=cap;
                    T req=e->flow-e->cap;
                    e->flow-=req;
                    e->rev->flow+=req;
                    ret-=req;
                    assert(cancel(dst,to,req));
                    assert(cancel(from,src,req));
                    if(e->cap==0&&e->rev->cap==0){
                        g[from].erase(e);
                        g[to].erase(e->rev);
                        exist[std::make_pair(from,to)]=0;
                        exist[std::make_pair(to,from)]=0;
                    }
                }
                return 1;
            }else{
                return 0;
            }
        }
    }

    void bfs(int s) {
        level.assign(n,-1);
        std::queue<int> q;
        level[s] = 0; q.push(s);
        while (!q.empty()) {
            int v = q.front(); q.pop();
            for(edge e: g[v]){
                if (e.cap-e.flow > 0 and level[e.to] < 0) {
                    level[e.to] = level[v] + 1;
                    q.push(e.to);
                }
            }
        }
    }

    T dfs(int v, int t,T f) {
        if (v == t) return f;
        for(auto &e=itr[v];e!=g[v].end();++e){
            if (e->cap-e->flow > 0 and level[v] < level[e->to]) {
                T d = dfs(e->to, t, std::min(f, e->cap-e->flow));
                if (d > 0) {
                    e->flow+=d;
                    e->rev->flow -= d;
                    return d;
                }
            }
        }
        return 0;
    }

    T __cancel(int v,int t,T f){
        if (v == t) return f;
        seen[v]=1;
        for (edge& e: g[v]){
            if (e.rev->flow > 0&&!seen[e.to]) {
                T d = __cancel(e.to, t, std::min(f,e.rev->flow));
                if (d > 0) {
                    e.flow+=d;
                    e.rev->flow-=d;
                    return d;
                }
            }
        }
        return 0;
    }
    T run() {
        T f;
        while (bfs(src), level[dst] >= 0) {
            for(int i=0;i<n;++i)itr[i]=g[i].begin();
            while ((f = dfs(src, dst, std::numeric_limits<T>::max())) > 0) {
                ret += f;
            }
        }
        return ret;
    }
    T cancel(int s,int t,T mx){
        T f;
        while(seen.assign(n,0),seen[s]=1,(f=__cancel(s, t, mx))>0)mx-=f;
        return mx==0;
    }
    T cap(int s,int t){
        if(exist[std::make_pair(s,t)]){
            return m[std::make_pair(s,t)]->cap;
        }else{
            return 0;
        }
    }
    T flow(int s,int t){
        if(exist[std::make_pair(s,t)]){
            return m[std::make_pair(s,t)]->flow;
        }else{
            return 0;
        }
    }
    void debug(){
        for(int i=0;i<n;++i)for(int j=0;j<n;++j){
            if(i==j)continue;
            if(flow(i,j)>0)std::cerr<<"("<<i<<","<<j<<")";
        }
        std::cerr<<'\n';
    }
};
#line 3 "code.cpp"

int main(){
    lint h,w;
    cin>>h>>w;
    mat v(h,vec(w,0));
    vector<lint>b;
    rep(i,h)rep(j,w){
        cin>>v[i][j];
        b.emplace_back(v[i][j]);
    }
    sort(all(b));
    b.erase(unique(all(b)),b.end());
    rep(i,h)rep(j,w)v[i][j]=lower_bound(all(b),v[i][j])-b.begin();
    lint n=b.size();
    vector<dinic<lint>>p(n);
    rep(i,n)p[i]=dinic<lint>(h+w+2,h+w,h+w+1);
    rep(i,h)rep(j,w){
        p[v[i][j]].add_edge(i,j+h,INF);
        p[v[i][j]].add_edge(j+h,i,INF);
    }
    rep(i,n){
        rep(j,h){
            p[i].add_edge(h+w,j,1);
        }
        rep(j,w){
            p[i].add_edge(j+h,h+w+1,1);
        }
    }
    lint ans=0;
    rep(i,n){
        if(b[i]){
            lint k=p[i].run();
            ans+=k;
        }
    }
    cout<<ans<<endl;
}