#include <iostream>
#include<vector>
#include<string>
#include<algorithm>
#include<iomanip>
#include<map>
#include<random>
#include<complex>
#include<math.h>
#include<functional>
#include<stack>
#include<queue>
#include<unordered_map>
#include<set>
#include<numeric>
#include <cassert>
using namespace std;
#define rep(i, n) for (int i = 0; i < (ll)(n); i++)
#define req(i,n) for(int i = 1;i <=  n; i++)
#define rrep(i,n) for(ll i = n-1;i >= 0;i--)
#define ALL(obj) begin(obj), end(obj)
#define RALL(a) rbegin(a),rend(a)
typedef long long ll;
typedef long double ld;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const int inf = 0x3fffffff;
const ll INF = 1e18;
struct UnionFind {
    vector<int> par;
    UnionFind(int n) : par(n, -1) { }
    void init(int n) { par.assign(n, -1); }
    int root(int x) {
        if (par[x] < 0) return x;
        else return par[x] = root(par[x]);
    }bool same(int x, int y) { return root(x) == root(y); }
    bool unite(int x, int y) {
        x = root(x); y = root(y);
        if (x == y) return false;
        if (par[x] > par[y]) swap(x, y); // merge technique
        par[x] += par[y]; par[y] = x;
        return 1;
    }int size(int x) { return -par[root(x)]; }
};
int main() {
    int n, m; cin >> n >> m; vector<int> b(n), c(n);
    UnionFind uf(n + m); ll sum = 0; vector<vector<int>> G(n);
    rep(i, n) {
        cin >> b[i] >> c[i], b[i]--, c[i]--;
        G[c[i]].push_back(b[i]);
    }rep(i, n) {
        rep(j, G[i].size() - 1) {
            int now = G[i][j], nx = G[i][j + 1];
            if (now != nx) uf.unite(now, nx);
        }
    }set<int> st;
    rep(i, m) st.insert(uf.root(i));
    for (int i : st) sum += uf.size(i) - 1;
    cout << sum << endl;
}