#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using vl = vector<ll>;
template<class T> using vc = vector<T>;
template<class T> using vvc = vector<vector<T>>;

#define eb emplace_back
#define all(x) (x).begin(), (x).end()
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define repr(i, n) for (ll i = (n)-1; i >= 0; i--)
#define repe(i, l, r) for (ll i = (l); i < (r); i++)
#define reper(i, l, r) for (ll i = (r)-1; i >= (l); i--)
#define repa(i,n) for (auto& i: n)

template<class T1, class T2> inline bool chmax(T1 &a, const T2 &b) {if (a<b) { a=b; return 1;} return 0;}
template<class T1, class T2> inline bool chmin(T1 &a, const T2 &b) {if (b<a) { a=b; return 1;} return 0;}
struct init{init(){cin.tie(0);ios::sync_with_stdio(false);cout<<fixed<<setprecision(15);}}init_;

#ifdef DEBUG
template <class T> void verr(const set<T> &st) { repa(a, st) cerr << a << " "; cerr << endl; }
template <class S, class T> void verr(const map<S, T> &mp) { repa(a, mp) cerr << "{" << a.first << ", " << a.second << "} "; cerr << endl; }
template <class S, class T, class N> void verr(const vector<pair<S,T>>& a, const N& n) { rep(i, n) cerr << "{" << a[i].first << ", " << a[i].second << "} "; cerr << endl; }
template <class T, class N> void verr(const vector<T>& a, const N& n) { rep(i, n) cerr << a[i] << " "; cerr << endl; }
ll dbgt = 1; void err() { cerr << "passed " << dbgt++ << endl; }
template<class H, class... T> void err(H&& h,T&&... t){ cerr<< h << (sizeof...(t)?" ":"\n") << flush; if(sizeof...(t)>0) err(forward<T>(t)...); }
#endif

const ll INF = 4e18;
const ld EPS = 1e-11;
const ld PI = acos(-1.0L);
const ll MOD = 1e9 + 7;
// const ll MOD = 998244353;
//--------------------------------------------------------------------------------//
struct UnionFind {
private:
    vector<int> par;
    vector<int> count;
    vector<int> rank;
public:
    UnionFind(int N) {
        count.assign(N, 1);
        rank.assign(N, 0);
        par.assign(N, 0);
        rep(i, N) par[i] = i;
    }

    int root(int x) {
        if (par[x] == x)
            return x;
        else {
            par[x] = root(par[x]);
            return par[x];
        }
    }

    void unite(int x, int y) {
        x = root(x), y = root(y);
        if (x == y) return;
        if (rank[x] < rank[y])
            swap(x, y);
        else if (rank[x] == rank[y])
            rank[y]++;
        par[y] = x;
        count[x] += count[y];
        return;
    }

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

    bool issame(int x, int y) {
        return root(x) == root(y);
    }
};
using UF = struct UnionFind;

int main() {
    ll N, M;
    cin >> N >> M;
    UF uf(M);
    vvc<ll> B(N);
    rep(i, N){
        ll b, c;
        cin >> b >> c, b--, c--;
        B[c].eb(b);
    }

    ll ans = 0;
    rep(i, N){
        if (B[i].size() <= 1) continue;
        ll a = B[i][0];
        repe(j, 1, B[i].size()){
            if (uf.issame(a, B[i][j])) continue;
            uf.unite(a, B[i][j]);
            ans++;
        }
    }

    cout << ans << endl;
}