#line 1 "a.cpp"
#include<iostream>
#include<vector>
using namespace std;
#line 2 "/home/kotatsugame/library/datastructure/UF.cpp"
struct UF{
	int n;
	vector<int>parent,rank;
	UF(int n_=0):n(n_),parent(n_),rank(n_,1)
	{
		for(int i=0;i<n_;i++)parent[i]=i;
	}
	int find(int a){return parent[a]!=a?parent[a]=find(parent[a]):a;}
	bool same(int a,int b){return find(a)==find(b);}
	bool unite(int a,int b)
	{
		a=find(a),b=find(b);
		if(a==b)return false;
		if(rank[a]<rank[b])
		{
			parent[a]=b;
			rank[b]+=rank[a];
		}
		else
		{
			parent[b]=a;
			rank[a]+=rank[b];
		}
		return true;
	}
	int size(int a){return rank[find(a)];}
};
#line 5 "a.cpp"
int N,M;
main()
{
	cin>>N>>M;
	UF uf(M);
	vector<vector<int> >G(N);
	for(int i=0;i<N;i++)
	{
		int b,c;cin>>b>>c;
		G[c-1].push_back(b-1);
	}
	int ans=0;
	for(vector<int>&v:G)
	{
		for(int i=1;i<v.size();i++)ans+=uf.unite(v[0],v[i]);
	}
	cout<<ans<<endl;
}