1 #include <stdio.h>
2 #include <iostream>
3 #include <algorithm>
4 #include <string.h>
5 #include <string>
6 #include <stdlib.h>
7 #include <math.h>
8 #include <time.h>
9
10 using namespace std;
11 typedef long long int LL;
12 const int INF=2e9+1e8;
13
14
15
16 const int maxn=1e6+10;
17
18
19 struct Date
20 {
21 double l,r,high;
22 int flag; //false 为 下面的边
23 } data[maxn];
24 double myh[maxn],input[maxn];
25 int n,k;
26 int getid(double x)
27 {
28 return lower_bound(myh+1,myh+k,x)-myh;
29 }
30 /**
31 *
32 * 线段树
33 *
34 */
35 struct Seg
36 {
37 int l,r,val;
38 double res;
39 } Tree[maxn];
40 void build(int i,int l,int r)
41 {
42 Tree[i].l=l,Tree[i].r=r;
43 Tree[i].val=0,Tree[i].res=0;
44 if(l==r) return ;
45 int mid=(l+r)>>1;
46 build(i<<1,l,mid);
47 build(i<<1|1,mid+1,r);
48 }
49 void deal(int i)
50 {
51 if(Tree[i].val) Tree[i].res=myh[Tree[i].r+1]-myh[Tree[i].l];
52 else if(Tree[i].l==Tree[i].r) Tree[i].res=0.;
53 else Tree[i].res=Tree[i<<1].res+Tree[i<<1|1].res;
54 }
55 void update(int i,int l,int r,int x) // 更新区间,并维护投影长度和,
56 {
57 if(l>r) return ;
58 if(Tree[i].l==l&&Tree[i].r==r)
59 {
60 Tree[i].val+=x;
61 deal(i);
62 return ;
63 }
64 int mid=(Tree[i].l+Tree[i].r)>>1;
65 if(r<=mid) update(i<<1,l,r,x);
66 else if(l>mid) update(i<<1|1,l,r,x);
67 else update(i<<1,l,mid,x),update(i<<1|1,mid+1,r,x);
68 deal(i);
69 }
70
71 double solve()
72 {
73 double ans=0;
74 update(1,getid(data[0].l),getid(data[0].r)-1,1);
75
76 for(int i=1; i<2*n; i++)
77 {
78 ans+=Tree[1].res*(data[i].high-data[i-1].high);
79 update(1,getid(data[i].l),getid(data[i].r)-1,data[i].flag);
80 }
81 return ans;
82 }
83 bool cmp(Date a,Date b)
84 {
85 return a.high<b.high;
86 }
87 int main()
88 {
89 // freopen("in.txt","r",stdin);
90 // freopen("out.txt","w",stdout);
91 while(scanf("%d",&n)!=EOF)
92 {
93 if(n==0) return 0;
94 for(int i=0; i<n; i++)
95 {
96 double x1,y1,x2,y2;
97 scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);
98 data[i].l=x1,data[i].r=x2,data[i].high=y1,data[i].flag=1;
99 data[n+i].l=x1,data[i+n].r=x2,data[n+i].high=y2,data[i+n].flag=-1;
100 input[i]=x1,input[i+n]=x2;
101 }
102 sort(data,data+2*n,cmp);// 对y进行排序;
103 sort(input,input+2*n);//将x进行排序,离散
104 k=1;
105 myh[k++]=input[0];
106 for(int i=1; i<2*n; i++)
107 if(input[i]!=input[i-1]) myh[k++]=input[i];
108 build(1,1,k-1);
109 printf("%.2lf\n",solve());
110 }
111 return 0;
112 }
