#include <bits/stdc++.h>
using namespace std;
using LL=long long;
using ULL=unsigned long long;
#define rep(i,n) for(int i=0; i<(n); i++)

struct dsu{
  vector<int> V;
  dsu(int n){ V.assign(n,-1); }
  int leader(int a){ return V[a]>=0?V[a]=leader(V[a]):a; }
  void merge(int r,int c){ if((c=leader(c))!=(r=leader(r))) V[c]=r; }
};


int N,M;
int B[200000];
int C[200000];

int main(){
  scanf("%d%d",&N,&M);
  rep(i,N){ scanf("%d%d",&B[i],&C[i]); B[i]--; C[i]--; }
  dsu G(N+M);
  rep(i,N) G.merge(C[i]+M,B[i]);
  vector<int> cnt(N);
  rep(i,M) if(G.leader(i)>=M) cnt[G.leader(i)-M]++;
  int ans=0; rep(i,N) ans+=max(0,cnt[i]-1);
  printf("%d\n",ans);
  return 0;
}