#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using ll = long long;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    ll n, m;
    cin >> n >> m;
    vector<pair<ll,ll>> edge(n);
    vector<ll> ca;
    ca.reserve(2 * n);
    for(auto &&[u, v] : edge){
        cin >> u >> v;
        ca.emplace_back(u);
        ca.emplace_back(v);
    }
    sort(ca.begin(), ca.end());
    ca.erase(unique(ca.begin(), ca.end()), ca.end());

    vector<int> cnt(ca.size());
    atcoder::dsu uf(ca.size());
    for(auto &&[u, v] : edge){
        u = lower_bound(ca.begin(), ca.end(), u) - ca.begin();
        v = lower_bound(ca.begin(), ca.end(), v) - ca.begin();
        uf.merge(u, v);
        cnt[u]++;
    }
    int ans = 0;
    auto G = uf.groups();
    for(auto &&vec : G){
        int tot = 0;
        for(auto &&v : vec){
            tot += cnt[v];
        }
        ans += min((int)vec.size(), tot);
    }
    cout << ans << '\n';
}