#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
using namespace std;

using ll = long long;
constexpr int INF = 1001001001;
constexpr int mod = 1000000007;
// constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

struct CountUnionFind{
    int sz;
    vector<int> par;
    vector<int> rank;
    vector<int> cnt;

    CountUnionFind(int n) : sz(n) {
        par.resize(sz);
        rank.assign(sz, 0);
        cnt.assign(sz, 1);
        for(int i = 0; i < sz; ++i){
            par[i] = i;
        }
    }

    int find(int x){
        if(par[x] == x) return x;
        else    return par[x] = find(par[x]);
    }

    bool same(int x, int y){
        return find(x) == find(y);
    }

    bool unite(int x, int y){
        x = find(x), y = find(y);
        if(x == y)  return false;
        if(rank[x] < rank[y]){
            par[x] = y;
            cnt[y] += cnt[x];
        }
        else{
            par[y] = x;
            cnt[x] += cnt[y];
            if(rank[x] == rank[y])  ++rank[x];
        }
        return true;
    }

    int get_cnt(int x){
        return cnt[find(x)];
    }
};

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N, M;
    cin >> N >> M;
    vector<vector<int>> color_to_box(N + 1);
    vector<bool> used(M + 1);
    for(int i = 0; i < N; ++i){
        int b, c;
        cin >> b >> c;
        color_to_box[c].emplace_back(b);
        used[b] = true;
    }
    CountUnionFind uf(M + 1);
    for(int i = 1; i <= N; ++i){
        int n = color_to_box[i].size();
        for(int j = 0; j + 1 < n; ++j){
            uf.unite(color_to_box[i][j], color_to_box[i][j + 1]);
        }
    }
    int ans = 0;
    for(int i = 1; i <= M; ++i){
        if(!used[i] || uf.find(i) != i) continue;
        ans += uf.get_cnt(i) - 1;
    }
    cout << ans << endl;

    return 0;
}