#include <bits/stdc++.h>
#include <atcoder/all>

using namespace std;
using namespace atcoder;

#define overload4(_1, _2, _3, _4, name, ...) name
#define rep1(n) for(int i = 0; i < (int)(n); ++i)
#define rep2(i, n) for(int i = 0; i < (int)(n); ++i)
#define rep3(i, a, b) for(int i = (a); i < (int)(b); ++i)
#define rep4(i, a, b, c) for(int i = (a); i < (int)(b); i += (c))
#define rep(...) overload4(__VA_ARGS__, rep4, rep3, rep2, rep1)(__VA_ARGS__)

#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; --i)
#define ALL(a) (a).begin(), (a).end()
#define Sort(a) (sort((a).begin(), (a).end()))
#define RSort(a) (sort((a).rbegin(), (a).rend()))
#define UNIQUE(a) (a.erase(unique((a).begin(), (a).end()), (a).end()))

typedef long long int ll;
typedef unsigned long long ul;
typedef long double ld;
typedef vector<int> vi;
typedef vector<long long> vll;
typedef vector<char> vc;
typedef vector<string> vst;
typedef vector<double> vd;
typedef vector<long double> vld;
typedef pair<long long, long long> P;

template<class T> long long sum(const T &a){ return accumulate(a.begin(), a.end(), 0LL); }
template<class T> auto min(const T &a){ return *min_element(a.begin(), a.end()); }
template<class T> auto max(const T &a){ return *max_element(a.begin(), a.end()); }

const long long MINF = 0x7fffffffffff;
const long long INF = 0x1fffffffffffffff;
const long long MOD = 998244353;
const long double EPS = 1e-9;
const long double PI = acos(-1);

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; }

template<typename T1, typename T2> istream &operator>>(istream &is, pair<T1, T2> &p){ is >> p.first >> p.second; return is; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){ os << "(" << p.first << ", " << p.second << ")"; return os; }
template<typename T> istream &operator>>(istream &is, vector<T> &v){ for(T &in : v) is >> in; return is; }
template<typename T> ostream &operator<<(ostream &os, const vector<T> &v){ for(int i = 0; i < (int) v.size(); ++i){ os << v[i] << (i + 1 != (int) v.size() ? " " : ""); } return os; }
template <typename T, typename S> ostream &operator<<(ostream &os, const map<T, S> &mp){ for(auto &[key, val] : mp){ os << key << ":" << val << " "; } return os; }
template <typename T> ostream &operator<<(ostream &os, const set<T> &st){ auto itr = st.begin(); for(int i = 0; i < (int) st.size(); ++i){ os << *itr << (i + 1 != (int) st.size() ? " " : ""); itr++; } return os; }
template <typename T> ostream &operator<<(ostream &os, const multiset<T> &st){ auto itr = st.begin(); for(int i = 0; i < (int) st.size(); ++i){ os << *itr << (i + 1 != (int) st.size() ? " " : ""); itr++; } return os; }
template <typename T> ostream &operator<<(ostream &os, queue<T> q){ while(q.size()){ os << q.front() << " "; q.pop(); } return os; }
template <typename T> ostream &operator<<(ostream &os, deque<T> q){ while(q.size()){ os << q.front() << " "; q.pop_front(); } return os; }
template <typename T> ostream &operator<<(ostream &os, stack<T> st){ while(st.size()){ os << st.top() << " "; st.pop(); } return os; }
template <class T, class Container, class Compare> ostream &operator<<(ostream &os, priority_queue<T, Container, Compare> pq){ while(pq.size()){ os << pq.top() << " "; pq.pop(); } return os; }

template <typename T>
long long binary_search(long long ok, long long ng, T check){
    while(abs(ok - ng) > 1){
        long long mid = (ok + ng) / 2;
        if(check(mid)) ok = mid;
        else ng = mid;
    }
    return ok;
}

template <typename T>
long double binary_search_real(long double ok, long double ng, T check, int iter = 100){
    for(int i = 0; i < iter; ++i){
        long double mid = (ok + ng) / 2;
        if(check(mid)) ok = mid;
        else ng = mid;
    }
    return ok;
}

template <typename T>
long long trisum(T a, T b){
    long long res = ((b - a + 1) * (a + b)) / 2;
    return res;
}

template <typename T>
T intpow(T x, int n){
    T ret = 1;
    while(n > 0) {
        if(n & 1) (ret *= x);
        (x *= x);
        n >>= 1;
    }
    return ret;
}

template <typename T>
T getReminder(T a, T b){
    if(b == 0) return -1;
    if(a >= 0 && b > 0){
        return a % b;
    } else if(a < 0 && b > 0){
        return ((a % b) + b) % b;
    } else if(a >= 0 && b < 0){
        return a % b;
    } else{
        return (abs(b) - abs(a % b)) % b;
    }
}

template<class T, class U> inline T vin(T &vec, U n) { vec.resize(n); for(int i = 0; i < (int) n; ++i) cin >> vec[i]; return vec; }
template<class T> inline void vout(T vec, string s = "\n"){ for(auto x : vec) cout << x << s; }
template<class... T> void in(T&... a){ (cin >> ... >> a); }
void out(){ cout << '\n'; }
template<class T, class... Ts> void out(const T &a, const Ts&... b){ cout << a; (cout << ... << (cout << ' ', b)); cout << '\n'; }
template<class T, class U> void inGraph(vector<vector<T>> &G, U n, U m, bool directed = false){ G.resize(n); for(int i = 0; i < m; ++i){ int a, b; cin >> a >> b; a--, b--; G[a].push_back(b); if(!directed) G[b].push_back(a); } }

template <typename T>
struct compress{
    std::vector<T> sorted;
    std::vector<int> compressed;

    compress(const std::vector<T> &vec){
        int n = vec.size();
        compressed.resize(n);
        for(T x : vec){
            sorted.emplace_back(x);
        }
        std::sort(sorted.begin(), sorted.end());
        sorted.erase(std::unique(sorted.begin(), sorted.end()), sorted.end());
        for(int i = 0; i < n; ++i){
            compressed[i] = std::lower_bound(sorted.begin(), sorted.end(), vec[i]) - sorted.begin();
        }
    }

    int get(const T &x) const{
        return std::lower_bound(sorted.begin(), sorted.end(), x) - sorted.begin();
    }

    T inv(const int x) const{
        return sorted[x];
    }

    size_t size() const{
        return sorted.size();
    }

    std::vector<int> getCompressed() const{
        return compressed;
    }
};

template<typename T>
struct Dinic{
private:
    int V;
    vector<int> level, iter;

    void bfs(int s, int t){
        fill(level.begin(), level.end(), -1);
        level[s] = 0;
        queue<int> q;
        q.push(s);
        while(!(q.empty())){
            int f = q.front();
            q.pop();
            for(auto &e : G[f]){
                if(e.cap > 0 && level[e.to] < 0){
                    level[e.to] = level[f] + 1;
                    if(e.to == t) return;
                    q.push(e.to);
                }
            }
        }
    }

    T dfs(int v, int t, T f){
        if(v == t){
            return f;
        }
        for(int &i = iter[v]; i < (int) G[v].size(); i++){
            edge &e = G[v][i];
            if(e.cap > 0 && level[v] < level[e.to]){
                T d = dfs(e.to, t, min(f, e.cap));
                if(d > 0){
                    e.cap -= d;
                    e.flow += d;
                    G[e.to][e.rev].cap += d;
                    G[e.to][e.rev].flow -= d;
                    return d;
                }
            }
        }
        return 0;
    }

public:
    struct edge{
        int to, rev;
        T cap, flow = 0;
    };
    vector<vector<edge>> G;

    Dinic(const int n) : V(n), level(n), iter(n), G(n){}

    void add_edge(int from, int to, T cap){
        G[from].push_back({to, (int) G[to].size(), cap});
        G[to].push_back({from, (int) G[from].size() - 1, (T) 0});
    }

    T flow(int s, int t){
        T flow = 0;
        while(true){
            bfs(s, t);
            if(level[t] < 0) return flow;
            fill(iter.begin(), iter.end(), 0);
            T f;
            while((f = dfs(s, t, numeric_limits<T>::max())) > 0){
                flow += f;
            }
        }
    }
};

ll T;

void input(){
    in(T);
}

void solve(){
    ll n, m; in(n, m);
    vll x(n), y(n);
    rep(i, n) in(x[i], y[i]);
    vll c;
    rep(i, n){
        c.push_back(x[i]);
        c.push_back(y[i]);
    }
    compress<ll> comp(c);
    ll len = comp.size();
    Dinic<ll> dinic(n + len + 2);
    ll s = n + len, t = s + 1;
    rep(i, n){
        dinic.add_edge(s, i, 1);
        dinic.add_edge(i, n + comp.get(x[i]), 1);
        dinic.add_edge(i, n + comp.get(y[i]), 1);
    }
    rep(i, len){
        dinic.add_edge(n + i, t, 1);
    }
    out(dinic.flow(s, t));
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(20);

    T = 1;
    // input();
    while(T--) solve();
}