#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
istream &operator>>(istream &is, modint &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint &a) { return os << a.val(); }
istream &operator>>(istream &is, modint998244353 &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint998244353 &a) { return os << a.val(); }
istream &operator>>(istream &is, modint1000000007 &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint1000000007 &a) { return os << a.val(); } 

typedef long long ll;
typedef vector<vector<int>> Graph;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define FOR(i,l,r) for (int i = l;i < (int)(r); i++)
#define rep(i,n) for (int i = 0;i < (int)(n); i++)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define my_sort(x) sort(x.begin(), x.end())
#define my_max(x) *max_element(all(x))
#define my_min(x) *min_element(all(x))
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; }
const int INF = (1<<30) - 1;
const ll LINF = (1LL<<62) - 1;
const int MOD = 998244353;
const int MOD2 = 1e9+7;
const double PI = acos(-1);
vector<int> di = {1,0,-1,0};
vector<int> dj = {0,1,0,-1};

#ifdef LOCAL
#  include <debug_print.hpp>
#  define debug(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define debug(...) (static_cast<void>(0))
#endif

int main(){
    cin.tie(0);
    ios_base::sync_with_stdio(false);
    ll N, M; cin >> N >> M;
    vector<ll> X(N), Y(N);
    vector<ll> Z(2 * N);
    rep(i, N){
        cin >> X[i] >> Y[i];
        Z[2 * i] = X[i];
        Z[2 * i + 1] = Y[i];
    }
    sort(all(Z));
    Z.erase(unique(all(Z)), Z.end());

    int L = Z.size();
    vector<vector<int>> g(L);
    vector<int> deg(L);
    rep(i, N){
        X[i] = lower_bound(all(Z), X[i]) - Z.begin();
        Y[i] = lower_bound(all(Z), Y[i]) - Z.begin();

        deg[X[i]]++;
        deg[Y[i]]++;
        g[X[i]].push_back(i);
        g[Y[i]].push_back(i);
    }

    int ans = 0;
    vector<int> vis(L), used(N);
    priority_queue<pii, vector<pii>, greater<pii>> pq;
    rep(i, L)if(deg[i]) pq.push({deg[i], i});

    while(!pq.empty()){
        auto [d, v] = pq.top();
        pq.pop();
        if(d != deg[v]) continue;

        assert(!vis[v]);
        ans += 1;
        vis[v] = 1;

        vector<tuple<int, int, int>> dat;
        for(auto id : g[v])if(!used[id]){
            int u = (v == X[id] ? Y[id] : X[id]);
            dat.push_back({(vis[u] ? INF : deg[u]), u, id});
        }

        int u = get<1>(dat[0]), id = get<2>(dat[0]);
        sort(rall(dat));
        used[id] = 1;
        deg[u] -= 1;
        if(deg[u] > 0 && !vis[u]){
            pq.push({deg[u], u});
        }
    }

    cout << ans << endl;
}