#include <bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) begin(v),end(v)
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
using ll = long long;
using pii = pair<int, int>;
constexpr ll INF = 1ll<<30;
constexpr ll longINF = 1ll<<60;
constexpr ll MOD = 1000000007;
constexpr bool debug = false;
//---------------------------------//

/**
 * @brief https://tkmst201.github.io/Library/DataStructure/UnionFind.hpp
 */
struct UnionFind {
public:
	using size_type = std::size_t;
	
private:
	size_type n;
	std::vector<int> dat;
	
public:
	UnionFind(size_type n) : n(n), dat(n, -1) {}
	
	size_type size(size_type x) {
		assert(x < n);
		return -dat[find(x)];
	}
	
	size_type find(size_type x) {
		assert(x < n);
		if (dat[x] < 0) return x;
		return dat[x] = find(dat[x]);
	}
	
	void unite(size_type x, size_type y) {
		assert(x < n);
		assert(y < n);
		x = find(x);
		y = find(y);
		if (x == y) return;
		if (dat[x] < dat[y]) std::swap(x, y);
		dat[x] += dat[y];
		dat[y] = x;
	}
	
	bool issame(size_type x, size_type y) {
		assert(x < n);
		assert(y < n);
		return find(x) == find(y);
	}
};

int main() {
	int N, M;
	cin >> N >> M;
	
	UnionFind uf(M);
	vector<int> box(N, -1);
	int ans = 0;
	REP(i, N) {
		int b, c;
		scanf("%d %d", &b, &c);
		--b; --c;
		if (box[c] != -1 && !uf.issame(b, box[c])) {
			uf.unite(b, box[c]);
			++ans;
		}
		box[c] = b;
	}
	cout << ans << endl;
}