#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define ALL(v) v.begin(), v.end()
typedef long long ll;

#include <bits/stdc++.h>
using namespace std;

class Dis{
  public:
  vector<ll> rank,p,siz;
  
  Dis(int s){
    rank.resize(s,0);
    p.resize(s,0);
    siz.resize(s,1);
    rep(i,s) makeSet(i);
  }
  
  void makeSet(int x){
    p[x]=x;
    rank[x]=0;
  }
  
  bool same(int x,int y){
    return findSet(x)==findSet(y);
  }
  
  void unite(int x,int y){
    if(same(x,y)) return;
    link(findSet(x),findSet(y));
  }
  
  void link(int x,int y){
    if(rank[x]>rank[y]){
      p[y]=x;
      siz[x]+=siz[y];
    }
    else{
      p[x]=y;
      siz[y]+=siz[x];
      if(rank[x]==rank[y]) rank[y]++;
    }
  }
  
  int findSet(int x){
    if(x != p[x]) p[x]=findSet(p[x]);
    return p[x];
  }
  
  int size(int x){
    return siz[findSet(x)];
  }
};


int main(){
  int n,m;
  cin>>n>>m;
  
  vector<int> A[n];
  rep(i,n){
    int b,c;
    cin>>b>>c;
    b--,c--;
    A[c].push_back(b);
  }
  
  Dis ds=Dis(m);
  rep(i,n){
    int t=A[i].size();
    if(t<2) continue;
    int tmp=A[i][0];
    for(int j=1;j<t;j++) ds.unite(tmp,A[i][j]);
  }
  int cnt=0;
  rep(i,m){
    if(ds.findSet(i)==i) cnt++;
  }
  cout<<m-cnt<<endl;
  
  return 0;
}