#include<bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using mint=modint998244353; //1000000007;
using ll=long long;
using pp=pair<int,int>;
#define sr string 
#define vc vector
#define fi first
#define se second
#define rep(i,n) for(int i=0;i<(int)n;i++)
#define pb push_back
#define all(v) v.begin(),v.end()
#define pque priority_queue
#define bpc(a) __builtin_popcount(a)
int main(){
  int h,w;cin>>h>>w;
  vc v(5e5+1,vc<pp>(0));
  rep(i,h)rep(j,w){
    int a;cin>>a;
    if(a)v[a].pb({i,j});
  }
  int ans=0;
  for(auto vx:v){
    if(!vx.size())continue;
    int n=vx.size();
    unordered_map<int,int>hm,wm;
    int ch=0,cw=0;
    for(auto [a,b]:vx)hm[a]=0,wm[b]=0;
    for(auto& [a,b]:hm)b=ch++;
    for(auto&[a,b]:wm)b=cw++;
    mf_graph<int>g(ch+cw+2);
    int sv=ch+cw; int gv=sv+1;
    for(auto [a,b]:vx)g.add_edge(hm[a],ch+wm[b],2);
    rep(i,ch)g.add_edge(sv,i,1);
    rep(i,cw)g.add_edge(ch+i,gv,1);
    int res=g.flow(sv,gv);
    ans+=res;
    //cout<<res<<' ';
  }
  cout<<ans;
}