// Get together

#include <stdio.h>
#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main() {
  int N, M;

  cin >> N >> M;

  vector<int> box;
  vector<pair<int, int> > color;

  for (int i = 0; i < N; i++) {
    int b, c;

    cin >> b >> c;

    b--; c--;

    box.push_back(b);
    color.push_back(make_pair(c, i));
  }

  sort(color.begin(), color.end());

  int ans = 0;

  for (int i = 1; i < N; i++) {
    int index = color[i].second;
    int bef = color[i - 1].second;

    if (color[i].first == color[i - 1].first
        && box[index] != box[bef]) {
      ans++;
      box[index] = box[bef];
    }
  }

  cout << ans << endl;

  return 0;
}