#include <iostream>
#include <vector>
using namespace std;

struct UnionFind
{
    std::vector<int> par, sz;
    
    UnionFind(int n){
        par.resize(n);
        sz.resize(n);
        for(int i = 0; i < n; i++){
            par[i] = i;
            sz[i] = 1;
        }
    }
    
    int find(int i){
        if(i == par[i]) return i;
        return par[i] = find(par[i]);
    }
    
    bool same(int i, int j){
        return find(i) == find(j);
    }
    
    void unite(int i, int j){
        i = find(i), j = find(j);
        if(i == j) return;
        if(sz[i] < sz[j]) std::swap(i, j);
        par[j] = i;
        sz[i] += sz[j];
    }
    
    int size(int i){
        return sz[find(i)];
    }
};

int main()
{
    int n, m;
    cin >> n >> m;
    vector<int> v[200005];
    for(int i = 0; i < n; i++){
        int b, c;
        cin >> b >> c;
        b--; c--;
        v[c].push_back(b);
    }
    UnionFind uf(m);
    for(int c = 0; c < n; c++){
        for(int j = 1; j < (int)v[c].size(); j++) uf.unite(v[c][0], v[c][j]);
    }
    int ans = 0;
    for(int i = 0; i < m; i++){
        if(uf.find(i) != i) ans++;
    }
    cout << ans << endl;
}