1 //扫描线矩形周长的并 POJ1177
2 // 我是按x轴
3
4 #include <iostream>
5 #include <cstdio>
6 #include <cstdlib>
7 #include <algorithm>
8 #include <vector>
9 #include <cmath>
10 #include <cstring>
11 // #include <memory.h>
12 // #include <bits/stdc++.h>
13 using namespace std;
14 #define LL long long
15 typedef pair<int,int> pii;
16 const LL inf = 0x3f3f3f3f;
17 const LL MOD =100000000LL;
18 const int N = 5010;
19 const double eps = 1e-5;
20 void fre() {freopen("in.txt","r",stdin);}
21 void freout() {freopen("out.txt","w",stdout);}
22 inline int read() {int x=0,f=1;char ch=getchar();while(ch>'9'||ch<'0') {if(ch=='-') f=-1; ch=getchar();}while(ch>='0'&&ch<='9') {x=x*10+ch-'0';ch=getchar();}return x*f;}
23
24 struct node{
25 int x1,x2,y;
26 int flag;
27 bool operator < (const node &a) const{
28 return y<a.y||(y==a.y&&flag>a.flag);
29 }
30 }e[N<<2];
31
32 int color[N<<3];
33 int sum[N<<3],hashh[N<<1];
34 int cnt[N<<3],pl[N<<3],pr[N<<3];
35 void pushup(int rt,int l,int r){
36 if(color[rt]) {
37 sum[rt]=hashh[r+1]-hashh[l];
38 cnt[rt]=1;
39 pl[rt]=pr[rt]=1;
40 }
41 else if(l!=r) {
42 sum[rt]=sum[rt<<1]+sum[rt<<1|1];
43 cnt[rt]=cnt[rt<<1]+cnt[rt<<1|1]-(pr[rt<<1]&&pl[rt<<1|1]);
44 pr[rt]=pr[rt<<1|1];
45 pl[rt]=pl[rt<<1];
46 }
47 else sum[rt]=cnt[rt]=pl[rt]=pr[rt]=0;
48 }
49 void update(int l,int r,int L,int R,int rt,int f){
50 if(l<=L&&R<=r){
51 color[rt]+=f;
52 pushup(rt,L,R);
53 return;
54 }
55 int mid=(L+R)>>1;
56 if(l<=mid) update(l,r,L,mid,rt<<1,f);
57 if(r>mid) update(l,r,mid+1,R,rt<<1|1,f);
58 pushup(rt,L,R);
59 }
60
61 int main(){
62 // fre();
63 int n;
64 scanf("%d",&n);
65 memset(color,0,sizeof(color));
66 memset(sum,0,sizeof(sum));
67 memset(cnt,0,sizeof(cnt));
68 memset(pr,0,sizeof(pr));
69 memset(pl,0,sizeof(pl));
70 int x1,x2,y1,y2;
71 for(int i=1;i<=n;i++){
72 scanf("%d%d%d%d",&x1,&y1,&x2,&y2);
73 e[i*2-1].x1=e[i*2].x1=x1;
74 e[i*2-1].x2=e[i*2].x2=x2;
75 e[i*2-1].y=y1,e[i*2].y=y2;
76 e[i*2-1].flag=1,e[i*2].flag=-1;
77 hashh[i*2-1]=x1,hashh[i*2]=x2;
78 }
79 sort(e+1,e+1+2*n);
80 sort(hashh+1,hashh+1+2*n);
81 int ans=0;
82 int lastsum=0;
83 e[0].y=e[1].y;
84 for(int i=1;i<=2*n;i++){
85 ans+=(e[i].y-e[i-1].y)*2*cnt[1];
86 int l=lower_bound(hashh+1,hashh+1+2*n,e[i].x1)-hashh;
87 int r=lower_bound(hashh+1,hashh+1+2*n,e[i].x2)-hashh-1;
88 if(l<=r) update(l,r,1,2*n,1,e[i].flag);
89 ans+=abs(sum[1]-lastsum);
90 lastsum=sum[1];
91 }
92 printf("%d\n",ans);
93 return 0;
94 }
