#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std;

#define REP(i, n) for (ll i = 0; i < n; i++)
#define REPR(i, n) for (ll i = n; i >= 0; i--)
#define FOR(i, m, n) for (ll i = m; i < n; i++)
#define FORR(i, m, n) for (ll i = m; i >= n; i--)
#define REPO(i, n) for (ll i = 1; i <= n; i++)
#define ll long long
#define INF (ll)1 << 60
#define MINF (-1 * INF)
#define ALL(n) n.begin(), n.end()
#define MOD 1000000007
#define P pair<ll, ll>

struct UnionFind {
	vector<int> data;
	UnionFind(int size) : data(size, -1) { }
	bool unionSet(int x, int y) {
		x = root(x); y = root(y);
		if (x != y) {
			if (data[y] < data[x]) swap(x, y);
			data[x] += data[y]; data[y] = x;
		}
		return x != y;
	}
	bool findSet(int x, int y) {
		return root(x) == root(y);
	}
	int root(int x) {
		return data[x] < 0 ? x : data[x] = root(data[x]);
	}
	int size(int x) {
		return -data[root(x)];
	}
};
ll n, m, ans;
bool used[210000];
UnionFind uf(210000);
vector<P> s;
int main(){
    cin >> n >> m;
	REP(i, n){
        ll a, b;
        cin >> a >> b;
        a--;
        b--;
        s.push_back(P(b, a));
    }
    sort(ALL(s));
	REP(i, (int)s.size() - 1){
        if (s[i].first == s[i + 1].first) uf.unionSet(s[i].second, s[i + 1].second);
    }
	REP(i, m){
		if(!used[uf.root(i)]){
            used[uf.root(i)] = true;
            ans++;
        }
	}
    cout << m - ans << endl;
}