#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 6 "cpplib/graph_tree/push_relabel.hpp"

/**
 * @brief 最大流(push_relabel法O(V^2√E))
 */
template<typename T>
class push_relabel{
    int n;
    T f=0;
    using i64=long long;
    struct edge{
        int from,to,rev;
        T flow,cap;
    };
    std::vector<i64>h,d;
    std::vector<std::vector<edge*>>g;
    std::vector<size_t>seen;
    std::priority_queue<std::pair<i64,int>,std::vector<std::pair<i64,int>>,std::greater<std::pair<i64,int>>>que;
    public:
    push_relabel(int n):n(n){
        h.resize(n,0);
        d.resize(n,0);
        g.resize(n);
        seen.resize(n,0);
    }
    void add_edge(int u,int v,T cap){
        g[u].emplace_back(new edge{u,v,(int)g[v].size(),0,cap});
        g[v].emplace_back(new edge{v,u,(int)g[u].size()-1,0,0});
    }
    void push(edge* e){
        int u=e->from,v=e->to;
        i64 df=std::min(d[u],e->cap-e->flow);
        e->flow+=df;
        g[v][e->rev]->flow-=df;
        d[u]-=df;
        d[v]+=df;
        if(d[v]>0)que.emplace(h[v],v);
        if(d[u]>0)que.emplace(h[u],u);
    }
    void relabel(int u){
        i64 mn=n*2;
        for(edge* e:g[u]){
            if(e->cap-e->flow>0){
                mn=std::min(mn,h[e->to]);
            }
        }
        h[u]=1+mn;
        que.emplace(h[u],u);
    }
    void discharge(int u){
        while(d[u]>0){
            if(seen[u]<g[u].size()){
                edge* e=g[u][seen[u]];
                if(e->cap-e->flow>0 && h[u]==h[e->to]+1){
                    push(e);
                }else{
                    seen[u]+=1;
                }
            }else{
                relabel(u);
                seen[u]=0;
            }
        }
    }
    T run(int s,int t){
        h[s]=n;
        for(auto e:g[s]){
            d[s]+=e->cap;
            push(e);
        }
        while(!que.empty()){
            int u=que.top().second;
            que.pop();
            if(u==s||u==t)continue;
            discharge(u);
        }
        for(auto e:g[s])f+=e->flow;
        return f;
    }
};
#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<push_relabel<lint>>p(n,0);
    rep(i,n)p[i]=push_relabel<lint>(h+w+2);
    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])ans+=p[i].run(h+w,h+w+1);
    }
    cout<<ans<<endl;
}