4 ЛКШ AC

#define pragma

#ifdef pragma
#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#endif // pragma

#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define ll long long
#define all(x) begin(x), end(x)
#define pb push_back
#define x first
#define y second
#define int long long
#define zero(two) memset(two, 0, sizeof(two))

using namespace std;
using namespace __gnu_pbds;


typedef vector<int> vi;
typedef vector<bool> vb;
typedef pair<int, int> pii;
typedef long double ld;
typedef vector<vi> matrix;
template<typename T>
using kawaii_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

const ld PI = atan2(0, -1);

void seriy() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cout << fixed << setprecision(10);
    #if _offline
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    #endif
}

const int MAXN = 2e3 + 10;
const int INF = 1e18 + 7;
const int MAXLOG = 20;
const int MOD = 998244353;
const int BASE = 47;

struct seg {
    pii a, b;
};

matrix g;
vi pr;
vb used;

bool cross(seg a, seg b) {
    if(a.a.x != a.b.x) {
        swap(a, b);
    }
    if(a.a.y <= b.a.y && a.b.y >= b.a.y || a.b.y <= b.a.y && a.a.y >= b.a.y) {
        if(a.a.x >= b.a.x && a.a.x <= b.b.x || a.a.x >= b.b.x && a.a.x <= b.a.x) {
            return 1;
        }
    }
    return 0;
}

bool kuhn(int u) {
    if(used[u]) return 0;
    used[u] = 1;
    for(auto v : g[u]) {
        if(pr[v] == -1 || kuhn(pr[v])) {
            pr[v] = u;
            return 1;
        }
    }
    return 0;
}

signed main() {
    seriy();
    int n;
    cin >> n;
    int cr[n][n];
    zero(cr);
    vi hor, ver;
    vector<seg> segs;
    for(int i = 0; i < n; i++) {
        int x, y, x1, y1;
        cin >> x >> y >> x1 >> y1;
        if(x == x1) {
            ver.pb(i);
        }
        else {
            hor.pb(i);
        }
        segs.pb({{x, y}, {x1, y1}});
    }
    g.resize(n);
    for(auto i : ver) {
        for(auto j : hor) {
            cr[i][j] = cross(segs[i], segs[j]);
            cr[j][i] = cross(segs[i], segs[j]);
            if(cr[i][j]) {
                g[i].pb(j);
                g[j].pb(i);
            }
        }
    }
    pr.resize(n, -1);
    used.resize(n);
    for(int i = 0; i < n; i++) {
        fill(all(used), 0);
        kuhn(i);
    }
    int cnt = 0;
    for(int i = 0; i < n; i++) {
//        cerr << pr[i] << " ";
        cnt += (pr[i] != -1);
    }
    cout << cnt / 2 + n - cnt;
    return 0;
}