#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------

int H,W;
int A[505][505];

template<int um> class UF {
	public:
	vector<int> par,rank,cnt;
	UF() {par=rank=vector<int>(um,0); cnt=vector<int>(um,1); for(int i=0;i<um;i++) par[i]=i;}
	void reinit(int num=um) {int i; FOR(i,num) rank[i]=0,cnt[i]=1,par[i]=i;}
	int operator[](int x) {return (par[x]==x)?(x):(par[x] = operator[](par[x]));}
	int count(int x) { return cnt[operator[](x)];}
	int operator()(int x,int y) {
		if((x=operator[](x))==(y=operator[](y))) return x;
		cnt[y]=cnt[x]=cnt[x]+cnt[y];
		if(rank[x]>rank[y]) return par[x]=y;
		rank[x]+=rank[x]==rank[y]; return par[y]=x;
	}
};
UF<505050> uf;

vector<pair<int,int>> E[505050];

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>H>>W;
	FOR(y,H) FOR(x,W) cin>>A[y][x];
	
	FOR(y,H) {
		map<int,int> M;
		FOR(x,W) if(A[y][x]) {
			if(M.count(A[y][x])) uf(M[A[y][x]],y*500+x);
			M[A[y][x]]=y*500+x;
		}
	}
	FOR(x,W) {
		map<int,int> M;
		FOR(y,H) if(A[y][x]) {
			if(M.count(A[y][x])) uf(M[A[y][x]],y*500+x);
			M[A[y][x]]=y*500+x;
		}
	}
	
	FOR(y,H) FOR(x,W) if(A[y][x]) E[uf[A[y][x]]].push_back({y,x});
	int ret=0;
	FOR(i,505040) if(E[i].size()) {
		set<int> R,C;
		FORR2(r,c,E[i]) R.insert(r),C.insert(c);
		ret+=min(R.size(),C.size());
	}
	
	cout<<ret<<endl;
	
	
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}