#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <numeric>
#include <functional>
#include <cassert>

#define debug_value(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << #x << "=" << x << endl;
#define debug(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << x << endl;

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; }

using namespace std;
typedef long long 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)];
    }
};

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    int n, m; cin >> n >> m;
    vector<vector<int>> v(n);
    vector<int> b(n), c(n);
    for(int i = 0; i < n; i++){
        cin >> b[i] >> c[i];
        b[i]--; c[i]--;
        v[c[i]].push_back(b[i]);
    }
    UnionFind uf(m);
    for(int i = 0; i < n; i++){
        for(int j = 0; j+1 < v[i].size(); j++){
            uf.unionSet(v[i][j], v[i][j+1]);
        }
    }
    int ans = 0;
    for(int i = 0; i < m; i++){
        if(uf.root(i) == i){
            ans += uf.size(i)-1;
        }
    }
    cout << ans << endl;
}