线段树--扫描线（模板）自下而上

#define IOS ios_base::sync_with_stdio(0); cin.tie(0);
#include <cstdio>//sprintf islower isupper
#include <cstdlib>//malloc  exit strcat itoa system("cls")
#include <iostream>//pair
#include <fstream>//freopen("C:\\Users\\13606\\Desktop\\草稿.txt","r",stdin);
#include <bitset>
//#include <map>
//#include<unordered_map>  https://www.luogu.org/problem/P5490
#include <vector>
#include <stack>
#include <set>
#include <string.h>//strstr substr
#include <string>
#include <time.h>//srand(((unsigned)time(NULL))); Seed n=rand()%10 - 0~9;
#include <cmath>
#include <deque>
#include <queue>//priority_queue<int, vector<int>, greater<int> > q;//less
#include <vector>//emplace_back
//#include <math.h>
//#include <windows.h>//reverse(a,a+len);// ~ ! ~ ! floor
#include <algorithm>//sort + unique : sz=unique(b+1,b+n+1)-(b+1);+nth_element(first, nth, last, compare)
using namespace std;//next_permutation(a+1,a+1+n);//prev_permutation
//******************
int abss(int a);
int lowbit(int n);
int Del_bit_1(int n);
int maxx(int a,int b);
int minn(int a,int b);
double fabss(double a);
void swapp(int &a,int &b);
clock_t __STRAT,__END;
double __TOTALTIME;
void _MS(){__STRAT=clock();}
void _ME(){__END=clock();__TOTALTIME=(double)(__END-__STRAT)/CLOCKS_PER_SEC;cout<<"Time: "<<__TOTALTIME<<" s"<<endl;}
//***********************
#define rint register int
#define fo(a,b,c) for(rint a=b;a<=c;++a)
#define fr(a,b,c) for(rint a=b;a>=c;--a)
#define mem(a,b) memset(a,b,sizeof(a))
#define pr printf
#define sc scanf
#define ls rt<<1
#define rs rt<<1|1
typedef long long ll;
const double E=2.718281828;
const double PI=acos(-1.0);
//const ll INF=(1LL<<60);
const int inf=(1<<30);
const double ESP=1e-9;
const int mod=(int)1e9+7;
const int N=(int)1e6+10;

struct node
{
    ll l,r,h;
    int f;
    friend bool operator<(node a,node b)
    {
        return a.h<b.h;
    }
}edge[N<<1];
ll temp[N<<1],res[N<<1];
int LS(int n)
{
    int m=0;
    for(int i=1;i<=n;++i)
        temp[++m]=res[i];
    sort(temp+1,temp+1+m);
    m=unique(temp+1,temp+1+m)-temp-1;
    for(int i=1;i<=n;++i)
        res[i]=lower_bound(temp+1,temp+1+m,res[i])-temp;
    return m;
}
struct
{
    ll l,r,cnt,sum;
}tr[N<<2];
void up(int rt)
{
    if(tr[rt].cnt) tr[rt].sum=temp[tr[rt].r+1]-temp[tr[rt].l];//因为是点之间的距离,而我代入的是
    else tr[rt].sum=tr[ls].sum+tr[rs].sum;                //线段前面的点,所以要加+1，向后移动一格;
}
void Build(int l,int r,int rt)
{
    tr[rt].l=l,tr[rt].r=r;
    if(l==r)return;
    int mid=(l+r)>>1;

    Build(l,mid,rt<<1);
    Build(mid+1,r,rt<<1|1);
    up(rt);
}
void update_qu(ll L,ll R,int V,int l,int r,int rt)
{
    if(L<=l&&r<=R)
    {
        tr[rt].cnt+=V;
        up(rt);
        return;
    }

    int mid=(l+r)>>1;
//    dn(rt,mid-l+1,r-mid);
    if(L<=mid)
        update_qu(L,R,V,l,mid,rt<<1);
    if(R>mid)
        update_qu(L,R,V,mid+1,r,rt<<1|1);
    up(rt);
}

int main()
{
//    freopen("D:\\Chrome Download\\testdata (3).in","r",stdin);
    int n;
    sc("%d",&n);
    for(int i=1;i<=n;++i)
    {
        int x1,y1,x2,y2;
        sc("%d%d%d%d",&x1,&y1,&x2,&y2);
        edge[i*2-1].h=y1;
        edge[i*2].h=y2;
        res[i*2-1]=x1;
        res[i*2]=x2;
    }
    int n_=LS(n*2);
    for(int i=1;i<=n;++i)
    {
        edge[2*i-1].l=edge[2*i].l=res[2*i-1];
        edge[2*i-1].r=edge[2*i].r=res[2*i];
        edge[i*2-1].f=1,edge[i*2].f=-1;
    }
    sort(edge+1,edge+1+2*n);
    Build(1,n_,1);
    update_qu(edge[1].l,edge[1].r-1,edge[1].f,1,n_,1);
    ll ans=0;
    ll th=edge[1].h;
    for(int i=2;i<=2*n;++i)
    {
        ans+=tr[1].sum*(edge[i].h-th);
        th=edge[i].h;
        update_qu(edge[i].l,edge[i].r-1,edge[i].f,1,n_,1);//因为是点之间的距离所以要减去;
    }                                                    //与80行对应;
    pr("%lld\n",ans);
    return 0;
}

/**************************************************************************************/

int maxx(int a,int b)
{
    return a>b?a:b;
}

void swapp(int &a,int &b)
{
    a^=b^=a^=b;
}

int lowbit(int n)
{
    return n&(-n);
}

int Del_bit_1(int n)
{
    return n&(n-1);
}

int abss(int a)
{
    return a>0?a:-a;
}

double fabss(double a)
{
    return a>0?a:-a;
}

int minn(int a,int b)
{
    return a<b?a:b;
}