Language: C++

#include<bits/stdc++.h>
#define all(x) (x).begin(),(x).end()
typedef long long ll;
#define rep(i,n) for(ll i=0, i##_len=(n); i<i##_len; ++i)
#define REP(i,num,n) for(ll i=num, i##_len=(n); i<i##_len; ++i)
#define repprev(i,a,b) for(ll i=b-1;i>=a;i--)
#define reprev(i,n) repprev(i,0,n)
using namespace std;
#define fore(i,a) for(auto &i:a)
#define sz(x) ((int)(x).size())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
#define MEMSET(v, h) memset((v), h, sizeof(v))
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
template<class T> int former(const vector<T> &v, T x){
   return upper_bound(v.begin(),v.end(),x) - v.begin() - 1;
}
template<class T> int latter(const vector<T> &v, T x){
    return lower_bound(v.begin(),v.end(),x) - v.begin();
}
#define pb push_back
#define mp make_pair
#define y0 y3487465
#define y1 y8687969
#define j0 j1347829
#define j1 j234892
#define BIT_FLAG_0 (1<<0) // 0000 0000 0000 0001
#define BIT_FLAG_1 (1<<1) // 0000 0000 0000 0010
#define BIT_FLAG_2 (1<<2) // 0000 0000 0000 0100
#define BIT_FLAG_3 (1<<3) // 0000 0000 0000 1000
#define BIT_FLAG_4 (1<<4) // 0000 0000 0001 0000
#define BIT_FLAG_5 (1<<5) // 0000 0000 0010 0000
#define BIT_FLAG_6 (1<<6) // 0000 0000 0100 0000
#define BIT_FLAG_7 (1<<7) // 0000 0000 1000 0000
ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
const ll INF = 1LL<<60;
 
const int MAX = 510000;
const int MOD = 1000000007;
 
long long fac[MAX], finv[MAX], inv[MAX];
 
// テーブルを作る前処理
void COMinit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++){
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}
 
// 二項係数計算
long long COM(int n, int k){
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}
 
struct UnionFind {
    vector<ll> par; // par[i]:iの親の番号　(例) par[3] = 2 : 3の親が2
 
    UnionFind(ll n) : par(n, -1) { }
    void init(ll n) { par.assign(n, -1); }
 
    ll root(ll x) {
        if (par[x] < 0) return x;
        else return par[x] = root(par[x]);
    }
 
    bool issame(ll x, ll y) {
        return root(x) == root(y);
    }
 
    bool merge(ll x, ll y) {
        x = root(x); y = root(y);
        if (x == y) return false;
        if (par[x] > par[y]) swap(x, y); // merge technique
        par[x] += par[y];
        par[y] = x;
        return true;
    }
 
    ll size(ll x) {
        return -par[root(x)];
    }
};
 
template <typename T>
vector<T> dijkstra(int s,vector<vector<pair<int, T> > > & G){
   const T INF = numeric_limits<T>::max();
   using P = pair<T, int>;
   int n=G.size();
   vector<T> d(n,INF);
   vector<int> b(n,-1);
   priority_queue<P,vector<P>,greater<P> > q;
   d[s]=0;
   q.emplace(d[s],s);
   while(!q.empty()){
     P p=q.top();q.pop();
     int v=p.second;
     if(d[v]<p.first) continue;
     for(auto& e:G[v]){
       int u=e.first;
       T c=e.second;
       if(d[u]>d[v]+c){
         d[u]=d[v]+c;
         b[u]=v;
         q.emplace(d[u],u);
       }
     }
   }
   return d;
}
 
const int dx[4] = {1, 0, -1, 0}; // const int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
const int dy[4] = {0, 1, 0, -1}; // const int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};

struct BipartiteMatching {
    vector<vector<int>> E; int n, m; vector<int> match, dist;
    void init(int _n,int _m){n=_n,m=_m;E.resize(n+m+2);match.resize(n+m+2);dist.resize(n+m+2);}
    bool bfs() {
        queue<int> que;
        REP(i, 1, n + 1) {
            if (!match[i]) dist[i] = 0, que.push(i);
            else dist[i] = INT_MAX;
        }
        dist[0] = INT_MAX;
        while (!que.empty()) {
            int u = que.front(); que.pop();
            if (u) fore(v, E[u]) if (dist[match[v]] == INT_MAX) {
                dist[match[v]] = dist[u] + 1;
                que.push(match[v]);
            }
        }
        return (dist[0] != INT_MAX);
    }
    bool dfs(int u) {
        if (u) {
            fore(v, E[u]) if (dist[match[v]] == dist[u] + 1) if (dfs(match[v])) {
                match[v] = u; match[u] = v;
                return true;
            }
            dist[u] = INT_MAX;
            return false;
        }
        return true;
    }
    void add(int a, int b) { b += n; E[a + 1].push_back(b + 1); E[b + 1].push_back(a + 1); }
    int whois(int x) { return match[x + 1] - 1; }
    int solve() {
        rep(i, n + m + 1) match[i] = 0;
        int res = 0;
        while (bfs()) REP(i, 1, n + 1) if (!match[i] && dfs(i)) res++;
        return res;
    }
};

void _main() {
  	ll N;
	cin >> N;
  	vector<ll> A(N);
  	vector<ll> B(N);
  	vector<ll> C(N);
	vector<ll> D(N);
    rep(i, N) cin >> A[i] >> B[i];
    rep(i, N) cin >> C[i] >> D[i];
 
    BipartiteMatching bm;
    bm.init(N, N);
    rep(i, N) rep(j, N) {
        if (A[i] < C[j] and B[i] < D[j]) bm.add(i, j);
    }
    cout << bm.solve() << endl;
}


Compiler output:
/usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/14/../../../x86_64-linux-gnu/Scrt1.o: in function `_start':
(.text+0x17): undefined reference to `main'
collect2: error: ld returned 1 exit status