#include<bits/stdc++.h>
// #include<atcoder/all>

using namespace std;
// using namespace atcoder;
using ll = long long;
using ull = unsigned long long;
using P = pair<int,int>;
#define rep(i,n) for(ll i = 0;i < (ll)n;i++)
#define ALL(x) (x).begin(),(x).end()
#define MOD 1000000007


// 2020/12/06 rechecked

class UnionFind{
  public:
  vector<int> par;
  UnionFind(long long size) : par(size,-1){}

  bool unite(int x,int y){
    x = root(x),y = root(y);
    if(x == y)return false;
    if(par[y] < par[x])swap(x,y);
    par[x] += par[y];
    par[y] = x;
    return true;
  }

  bool find(int x,int y){
    return root(x) == root(y);
  }

  int root(int x){
    return par[x] < 0 ? x : par[x] = root(par[x]);
  }

  int size(int x){
    return -par[root(x)];
  }
};


int main(){
  
  int n,m;
  cin >> n >> m;
  UnionFind uf(m);
  vector<int> col(n,-1);
  rep(i,n){
    int b,c;cin >> b >> c;
    b--;c--;
    if(col[c] >= 0)uf.unite(col[c],b);
    else col[c] = b;
  }
  int res = 0;
  rep(i,m)if(uf.root(i) == i)res += uf.size(i)-1;
  cout << res << "\n";


  return 0;
}