ЗОШ объедини прямоуг-ки OK

#include <iostream>
#include <cmath>
#include <vector>
#include <queue>
#include <algorithm>
#include <string>
#include <stack>
#include <set>
#include <map>
#define pii pair <int,int>
using namespace std;
using ll = long long;
using ld = long double;
void cv(vector <int> &v){
    for (auto x: v) cout<<x<<' ';
    cout<<"\n";
}

void cvl(vector <ll> &v){
    for (auto x: v) cout<<x<<' ';
    cout<<"\n";
}


void cvv(vector <vector <int> > &v){
    for (auto x: v) cv(x);
    cout<<"\n";
}

struct hpny{
    int y, tp;
};

struct hpnx{
    int x,tp; //0-открыл, 1  -закрыл
    hpny y1, y2;
};

void shx(hpnx sm){
    cout<<"x = "<<sm.x<<"\n";
    cout<<"type = "<<sm.tp<<"\n";
    cout<<"\n";
}

void shy(hpny sm){
    cout<<"y = "<<sm.y<<"\n";
    cout<<"type = "<<sm.tp<<"\n";
    cout<<"\n";
}

vector <hpnx> allx;

vector <hpny> ally;//now


bool cmpx(hpnx a, hpnx b){
    return a.x < b.x;
}

bool cmpy(hpny a, hpny b){
    return a.y < b.y;
}

ll ans=0;
int x1, x2;
int idx = 1;
//scan y
ll scy(){ //x join
    ll join = 0;
    int bly = 1;
    for (int i = 1; i < ally.size();++i){

        if (bly > 0){
            join += ally[i].y - ally[i-1].y;
        }
        if (ally[i].tp == 0){
            bly++;
        }
        else{
            bly--;
        }

    }

    ans += (x2 - x1) * join;
}

int main()
{
    ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int n; cin>>n;
	for (int i=0;i<n;++i){
        int x1, y1, x2, y2;
        cin>>x1>>y1>>x2>>y2;
        hpnx xl, xr;
        hpny yl, yr;
        yl = {y1, 0};
        yr = {y2, 1};
        xl = {x1, 0, yl, yr};
        xr = {x2, 1, yl, yr};
        allx.push_back(xl);
        allx.push_back(xr);
	}
	sort(allx.begin(), allx.end(), cmpx);
	int blx = 1;

	x1 = allx[0].x;
	ally.push_back(allx[0].y1);
	ally.push_back(allx[0].y2);
	while (idx < n * 2) {
        x2 = allx[idx].x;
        scy();
        if (allx[idx].tp == 1){
            blx--;
            int id1, id2;
            for (int j = 0; j < ally.size();++j){
                if (ally[j].y == allx[idx].y1.y && ally[j].tp == 0){
                    id1 = j;
                }
                else if (ally[j].y == allx[idx].y2.y && ally[j].tp == 1){
                    id2 = j;
                }
            }
            ally.erase(ally.begin() + id1);
            id2--;
            ally.erase(ally.begin() + id2);
        }




        if (allx[idx].tp == 0){
            blx++;
            ally.push_back(allx[idx].y1);
            ally.push_back(allx[idx].y2);
            sort(ally.begin(), ally.end(), cmpy);
        }

        x1 = x2;

        idx++;
	}
	//cout<<"ans = "<<ans<<"\n";
	cout<<ans<<"\n";
}
/*
3
1 1 3 5
5 2 7 4
2 4 6 7

4
1 1 3 5
5 2 7 4
2 4 6 7
10 0 20 10

5
1 1 3 5
5 2 7 4
2 4 6 7
10 0 20 10
0 9 15 10
*/