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

struct Unionfind {
  // tree number
  vector<int> par;
  // constructor
  Unionfind(int n = 1) : par(n, -1) {}
  // search root
  int root(int x) {
    if (par[x] < 0) return x;
    return par[x] = root(par[x]);
  }
  // is same?
  bool issame(int x, int y) { return root(x) == root(y); }

  // add
  // already added, return 0
  bool uni(int x, int y) {
    x = root(x);
    y = root(y);
    if (x == y) return 0;
    if (par[x] > par[y]) swap(x, y);
    par[x] += par[y];
    par[y] = x;
    return 1;
  }
  int size(int x) { return -par[root(x)]; }
};

int n, m;
Unionfind uf;
vector<int> v;

int main() {
  cin >> n >> m;
  uf = Unionfind(m);
  v.assign(n, -1);
  int res = 0;
  for (int i = 0; i < n; ++i) {
    int b, c;
    cin >> b >> c;
    --b, --c;
    if (v[c] >= 0) {
      if (!uf.issame(b, v[c])) ++res, uf.uni(b, v[c]);
    } else
      v[c] = b;
  }
  cout << res << endl;
  return 0;
}