#include<bits/stdc++.h>
// #include<atcoder/all>
using namespace std;
using lint = long long;
template<class T>using graph = vector<vector<T>>;
#define endl '\n'
int const INF = 1<<30;
lint const INF64 = 1LL<<62;
lint const mod = 1e9+7;
//long const mod = 998244353;
#ifndef ATCODER_DSU_HPP
#define ATCODER_DSU_HPP 1

#include <algorithm>
#include <cassert>
#include <vector>

namespace atcoder {

// Implement (union by size) + (path compression)
// Reference:
// Zvi Galil and Giuseppe F. Italiano,
// Data structures and algorithms for disjoint set union problems
struct dsu {
  public:
    dsu() : _n(0) {}
    dsu(int n) : _n(n), parent_or_size(n, -1) {}

    int merge(int a, int b) {
        assert(0 <= a && a < _n);
        assert(0 <= b && b < _n);
        int x = leader(a), y = leader(b);
        if (x == y) return x;
        if (-parent_or_size[x] < -parent_or_size[y]) std::swap(x, y);
        parent_or_size[x] += parent_or_size[y];
        parent_or_size[y] = x;
        return x;
    }

    bool same(int a, int b) {
        assert(0 <= a && a < _n);
        assert(0 <= b && b < _n);
        return leader(a) == leader(b);
    }

    int leader(int a) {
        assert(0 <= a && a < _n);
        if (parent_or_size[a] < 0) return a;
        return parent_or_size[a] = leader(parent_or_size[a]);
    }

    int size(int a) {
        assert(0 <= a && a < _n);
        return -parent_or_size[leader(a)];
    }

    std::vector<std::vector<int>> groups() {
        std::vector<int> leader_buf(_n), group_size(_n);
        for (int i = 0; i < _n; i++) {
            leader_buf[i] = leader(i);
            group_size[leader_buf[i]]++;
        }
        std::vector<std::vector<int>> result(_n);
        for (int i = 0; i < _n; i++) {
            result[i].reserve(group_size[i]);
        }
        for (int i = 0; i < _n; i++) {
            result[leader_buf[i]].push_back(i);
        }
        result.erase(
            std::remove_if(result.begin(), result.end(),
                           [&](const std::vector<int>& v) { return v.empty(); }),
            result.end());
        return result;
    }

  private:
    int _n;
    // root node: -1 * component size
    // otherwise: parent
    std::vector<int> parent_or_size;
};

}  // namespace atcoder

#endif  // ATCODER_DSU_HPP


int main(){

using namespace atcoder;
    lint n,m;
    cin >> n >> m;
    lint b[n],c[n];
    for(int i=0;i<n;i++){
        cin >> b[i]  >> c[i];
        b[i]--;
        c[i]--;
    }
    vector<vector<lint>>colors(n);
    vector<lint>cnt(n);
    for(int i=0;i<n;i++){
        colors[c[i]].push_back(b[i]);
    }
    lint ans = 0;
    dsu d(m);
    for(int i=0;i<n;i++){
        for(int j=0;j+1<colors[i].size();j++){
            if(!d.same(colors[i][j], colors[i][j+1])){
                d.merge(colors[i][j], colors[i][j+1]);
                ans++;
            }
        }
    }
    cout << ans << endl;
}