1 #include <cstdio>
  2 #include <cstring>
  3 #include <algorithm>
  4 #include <iostream>
  5 #include <vector>
  6 #include <queue>
  7 #include <cmath>
  8 #include <set>
  9 using namespace std;
 10 
 11 #define N 50005
 12 #define ll root<<1
 13 #define rr root<<1|1
 14 #define mid (a[root].l+a[root].r)/2
 15 
 16 int max(int x,int y){return x>y?x:y;}
 17 int min(int x,int y){return x<y?x:y;}
 18 int abs(int x,int y){return x<0?-x:x;}
 19 
 20 struct node{
 21     int l, r;
 22     int val;
 23     __int64 sum;
 24 }a[N*16];
 25 
 26 struct Line{
 27     int x1, x2, y;
 28     int val;
 29     Line(){}
 30     Line(int a,int b,int c,int d){
 31         x1=a;
 32         x2=b;
 33         y=c;
 34         val=d;
 35     }
 36 }line[N*8];
 37 
 38 bool cmp(Line a,Line b){
 39     return a.y<b.y;
 40 }
 41 
 42 int xx[N*4];
 43 int n, m;
 44 
 45 int b_s(int key){
 46     int l=1, r=m;
 47     while(l<=r){
 48         int mm=(l+r)/2;
 49         if(xx[mm]==key) return mm;
 50         else if(xx[mm]<key) l=mm+1;
 51         else if(xx[mm]>key) r=mm-1;
 52     }
 53 }
 54 
 55 void build(int l,int r,int root){
 56     a[root].l=l;
 57     a[root].r=r;
 58     a[root].sum=a[root].val=0;
 59     if(l==r) return;
 60     build(l,mid,ll);
 61     build(mid+1,r,rr);
 62 }
 63 
 64 void up(int root){
 65     if(a[root].val) a[root].sum=xx[a[root].r+1]-xx[a[root].l];
 66     else if(a[root].l==a[root].r) a[root].sum=0;
 67     else a[root].sum=a[ll].sum+a[rr].sum;
 68 }
 69 
 70 void update(int l,int r,int val,int root){
 71     if(l>r) return;
 72     if(a[root].l==l&&a[root].r==r){
 73         a[root].val+=val;
 74         up(root);
 75         return;
 76     }
 77     if(r<=a[ll].r) update(l,r,val,ll);
 78     else if(l>=a[rr].l) update(l,r,val,rr);
 79     else{
 80         update(l,mid,val,ll);
 81         update(mid+1,r,val,rr);
 82     }
 83     up(root);
 84 }
 85 main()
 86 {
 87     int x1, y1, x2, y2, x3, y3, x4, y4;
 88     int i, j, k;
 89     while(scanf("%d",&n)&&n){
 90         k=0;
 91         m=1;
 92         for(i=0;i<n;i++){
 93             scanf("%d %d %d %d %d %d %d %d",&x1,&y1,&x2,&y2,&x3,&y3,&x4,&y4);
 94             line[k++]=Line(x1,x3,y1,1);
 95             line[k++]=Line(x1,x3,y2,-1);
 96             line[k++]=Line(x3,x4,y1,1);
 97             line[k++]=Line(x3,x4,y3,-1);
 98             line[k++]=Line(x3,x4,y4,1);
 99             line[k++]=Line(x3,x4,y2,-1);
100             line[k++]=Line(x4,x2,y1,1);
101             line[k++]=Line(x4,x2,y2,-1);
102             xx[m++]=x1;
103             xx[m++]=x2;
104             xx[m++]=x3;
105             xx[m++]=x4;
106         }
107         sort(xx+1,xx+m);
108         m=unique(xx+1,xx+m)-xx-1;
109         sort(line,line+k,cmp);
110         build(1,m,1);
111         __int64 ans=0;
112         for(i=0;i<k-1;i++){
113             update(b_s(line[i].x1),b_s(line[i].x2)-1,line[i].val,1);
114             ans+=a[1].sum*(__int64)(line[i+1].y-line[i].y);
115         }
116         printf("%I64d\n",ans);
117     }
118 }