#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int INF = 1e9 + 10;
const ll INFL = 4e18;

#include <atcoder/maxflow>

int main() {
    ll N, M;
    cin >> N >> M;
    vector<ll> X(N), Y(N), V;
    for (int i = 0; i < N; i++) cin >> X[i] >> Y[i], V.push_back(X[i]), V.push_back(Y[i]);

    ranges::sort(V);
    V.erase(unique(V.begin(), V.end()), V.end());
    auto get = [&](ll x) { return ranges::lower_bound(V, x) - V.begin(); };
    int S = ssize(V);

    int T = N + M + 2, s = N + M, t = N + M + 1;
    atcoder::mf_graph<int> mf(T);
    for (int i = 0; i < N; i++) mf.add_edge(s, i, 1);
    for (int i = N; i < N + S; i++) mf.add_edge(i, t, 1);
    for (int i = 0; i < N; i++) mf.add_edge(i, N + get(X[i]), 1), mf.add_edge(i, N + get(Y[i]), 1);

    cout << mf.flow(s, t) << endl;
}