#include<bits/stdc++.h>
#define int long long
using namespace std;
struct UnionFind{
    vector<int>par;
    UnionFind(int n):par(n,-1){}
    int find(int x){return par[x]<0?x:par[x]=find(par[x]);}
    void merge(int x,int y){
        x=find(x);y=find(y);
        if(x==y)return;
        if(par[x]>par[y])swap(x,y);
        par[x]+=par[y];par[y]=x;
    }
    int size(int x){return max(-par[x],1ll);}
};
signed main(){
    int N,M;cin>>N>>M;
    vector<vector<int>>V(N);
    for(int i=0;i<N;i++){
        int b,c;cin>>b>>c;
        V[--c].push_back(--b);
    }
    UnionFind UF(M);
    for(int i=0;i<N;i++){
        for(int j:V[i])UF.merge(j,V[i][0]);
    }
    int ans=0;
    for(int i=0;i<M;i++)ans+=UF.size(i)-1;
    cout<<ans<<endl;
}