/**
*    author:  tomo0608
*    created: 13.02.2021 00:11:35
**/

#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef long double ld;
template <class T> using V = vector<T>;
template <class T> using VV = V<V<T>>;
typedef pair<int,int> pii;
typedef pair<long long, long long> pll;

#define all(x) x.begin(),x.end()
#define rep2(i, m, n) for (int i = (m); i < (n); ++i)
#define rep(i, n) rep2(i, 0, n)
#define drep2(i, m, n) for (int i = (m)-1; i >= (n); --i)
#define drep(i, n) drep2(i, n, 0)
#define unique(a) a.erase(unique(a.begin(),a.end()),a.end())
template<class T> using priority_queue_rev = priority_queue<T, vector<T>, greater<T> >;
template<class T, class U> inline bool chmax(T &a, const U &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T, class U> inline bool chmin(T &a, const U &b) { if (a>b) { a=b; return 1; } return 0; }
template<class T1, class T2> istream &operator>>(istream &is, pair<T1, T2> &p) { is >> p.first >> p.second; return is; }
template<class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p) { os << '(' << p.first << ", " << p.second << ')'; return os; }
template<class T> istream &operator>>(istream &is, vector<T> &v) { for (auto &e : v) is >> e; return is; }
template<class T> ostream &operator<<(ostream &os, const vector<T> &v) { for (auto &e : v) os << e << ' '; return os; }
template<typename T> ostream& operator << (ostream& os, set<T>& set_var) {os << "{"; for (auto itr = set_var.begin(); itr != set_var.end(); itr++) {os << *itr;++itr;if(itr != set_var.end()) os << ", ";itr--;}os << "}";return os;}
template <typename T, typename U> ostream &operator<<(ostream &os, map<T, U> &map_var) {os << "{";for(auto itr = map_var.begin(); itr != map_var.end(); itr++) {os << *itr;itr++;if (itr != map_var.end()) os << ", ";itr--;}os << "}";return os;}
template<class T> inline int count_between(vector<T> &a, T l, T r) { return lower_bound(all(a), r) - lower_bound(all(a), l); } // [l, r)
#define pb push_back
#define eb emplace_back
#define elif else if
#define mp make_pair
#define bit(n, k) ((n >> k) & 1) /*nのk bit目*/
template<typename T> T gcd(T x, T y){if(x%y == 0)return y;return gcd(y, x%y);}
template<typename T> T gcd(vector<T> a){T res = a[0];for(auto &x: a)res = gcd(res, x);return res;}
template <typename T>T mypow(T x, ll n){T ret = 1;while(n > 0){if(n & 1)(ret *= x);(x *= x);n >>= 1;}return ret;}
#define endl '\n'
int dx[8] = {1, 0, -1, 0, 1, 1, -1, -1};
int dy[8] = {0, 1, 0, -1, 1, -1, -1, 1};

// Primality test
class Prime {
    public:
    const int N;
    vector<int> min_prime;
    vector<int> primes;
    Prime(int size): N(size), min_prime(N+1){
        rep(i,N+1)min_prime[i] = i;
        min_prime[0] = -1;
        min_prime[1] = -1;
        for(int i = 2;i<=N;i++){
            if(min_prime[i]!=i)continue;
            primes.push_back(i);
            int tmp = 2*i;
            while(tmp <= N){
                if(min_prime[tmp]==tmp)min_prime[tmp] = i;
                tmp += i;
            }
        }
    }
    bool check(int x){ return min_prime[x] == x;}
};

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

namespace atcoder {

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;
    std::vector<int> parent_or_size;
};

}  // namespace atcoder


void solve(){
    int n,m;cin >> n >> m;
    V<int> col(n, -1);
    atcoder::dsu uf(m);
    rep(i,n){
        int b,c;cin >> b >> c;
        b--;
        c--;
        if(col[c] != -1){
            uf.merge(b, col[c]);
        }
        col[c] = b;
    }
    ll ans = 0;
    rep(i,m)if(uf.leader(i) == i)ans += uf.size(i)-1;
    cout << ans << endl;
}

int main() {
    cin.tie(0);
    ios_base::sync_with_stdio(false);
    cout << setprecision(20);
    int codeforces = 1;
    //cin >> codeforces;
    while(codeforces--){
        solve();
    }
    return 0;
}