1 #include<cstdio>
2 #include<cstring>
3 #include<cstdlib>
4 #define MAXN 50010
5 typedef __int64 LL;
6 struct Line
7 {
8 int left,right,high,flag;
9 };
10 struct node
11 {
12 int cover,len;
13 };
14 Line p[MAXN<<3];
15 node tree[MAXN<<5];
16 int cnt,x[MAXN<<3];
17 inline void Post(int x1,int y1,int x2,int y2)
18 {
19 if(x1!=x2&&y1!=y2)
20 {
21 x[cnt]=x1;
22 p[cnt].left=x1;
23 p[cnt].right=x2;
24 p[cnt].high=y1;
25 p[cnt++].flag=1;
26 x[cnt]=x2;
27 p[cnt].left=x1;
28 p[cnt].right=x2;
29 p[cnt].high=y2;
30 p[cnt++].flag=-1;
31 }
32 }
33 int cmp1(const void *a,const void *b)
34 {
35 return *(int *)a-*(int *)b;
36 }
37 int cmp2(const void *a,const void *b)
38 {
39 return (*(Line *)a).high-(*(Line *)b).high;
40 }
41 int Bin(int val,int low,int high)
42 {
43 int mid;
44 while(low<high)
45 {
46 mid=(low+high)>>1;
47 if(x[mid]==val)
48 return mid;
49 if(x[mid]<val)
50 low=mid+1;
51 else
52 high=mid;
53 }
54 }
55 void Build(int L,int R,int rt)
56 {
57 tree[rt].len=tree[rt].cover=0;
58 if(L!=R)
59 {
60 int mid=(L+R)>>1;
61 Build(L,mid,rt<<1);
62 Build(mid+1,R,rt<<1|1);
63 }
64 }
65 inline void PushUp(int L,int R,int rt)
66 {
67 if(tree[rt].cover)
68 tree[rt].len=x[R+1]-x[L];
69 else if(L==R)
70 tree[rt].len=0;
71 else
72 tree[rt].len=tree[rt<<1].len+tree[rt<<1|1].len;
73 }
74 void Update(int st,int en,int flag,int L,int R,int rt)
75 {
76 if(st<=L&&R<=en)
77 {
78 tree[rt].cover+=flag;
79 PushUp(L,R,rt);
80 }
81 else
82 {
83 int mid=(L+R)>>1;
84 if(mid>=st)
85 Update(st,en,flag,L,mid,rt<<1);
86 if(en>mid)
87 Update(st,en,flag,mid+1,R,rt<<1|1);
88 PushUp(L,R,rt);
89 }
90 }
91 int main()
92 {
93 LL ans;
94 int i,n,m,st,en,x1,y1,x2,y2,x3,y3,x4,y4;
95 while(scanf("%d",&n),n)
96 {
97 for(cnt=i=0;i<n;i++)
98 {
99 scanf("%d%d%d%d%d%d%d%d",&x1,&y1,&x2,&y2,&x3,&y3,&x4,&y4);
100 Post(x1,y1,x2,y3);
101 Post(x1,y4,x2,y2);
102 Post(x1,y3,x3,y4);
103 Post(x4,y3,x2,y4);
104 }
105 qsort(x,cnt,sizeof(x[0]),cmp1);
106 qsort(p,cnt,sizeof(p[0]),cmp2);
107 for(i=m=0;i<cnt;i++)
108 {
109 if(x[i]!=x[m])
110 x[++m]=x[i];
111 }
112 Build(0,m,1);
113 for(ans=i=0;i<cnt-1;i++)
114 {
115 st=Bin(p[i].left,0,m+1);
116 en=Bin(p[i].right,0,m+1);
117 Update(st,en-1,p[i].flag,0,m,1);
118 ans+=(LL)(p[i+1].high-p[i].high)*tree[1].len;
119 }
120 printf("%I64d\n",ans);
121 }
122 return 0;
123 }
