#include <cstdio>#include <iostream>#include <algorithm>#include <cstdio>#include <queue>#include <iostream>#include <cstring>#define INF 9999999using namespace std;struct Seg{int l;int r;int y;int v;Seg(int L,int R,int Y,int V):l(L),r(R),y(Y),v(V){}Seg(){}bool operator<(const Seg& s) const {if(y != s.y)return y < s.y;else return v > s.v;}}ss[50050 << 2];int length[50050 << 2];int nLayer[50050 << 2];void calc(int index,int l,int r){if(nLayer[index])length[index] = r - l + 1;else if(l == r)length[index] = 0;elselength[index] = length[index<<1] + length[index<<1|1];}void PullUp(int index,int l,int r){if(nLayer[index << 1] && nLayer[index << 1|1]){int tmp = (nLayer[index<<1] < nLayer[index<<1|1]) ? nLayer[index<<1] : nLayer[index<<1|1];nLayer[index] = tmp;nLayer[index<<1] -= tmp;nLayer[index<<1|1] -= tmp;int mid = (l+r) >>1;calc(index<<1,l,mid);calc(index<<1|1,mid+1,r);}}void PushDown(int index,int l,int r){if(nLayer[index]){nLayer[index<<1] += nLayer[index];nLayer[index<<1|1] += nLayer[index];int mid = (l + r) >> 1;calc(index<<1,l,mid);calc(index<<1|1,mid + 1,r);nLayer[index] = 0;calc(index,l,r);}}void update(int a,int b,int v,int l,int r,int index){if(a<=l && r<=b){nLayer[index] += v;calc(index,l,r);return;}PushDown(index,l,r);int mid = (l + r) >> 1;if(a <= mid)update(a,b,v,l,mid,index<<1);if(b > mid)update(a,b,v,mid+1,r,index<<1|1);PullUp(index,l,r);calc(index,l,r);}int main(){int N;while(scanf("%d",&N) && N){int m = 0;memset(length,0,sizeof(length));memset(nLayer,0,sizeof(nLayer));for(int i = 0; i < N; ++i){int x1,y1,x2,y2,x3,y3,x4,y4;scanf("%d%d%d%d%d%d%d%d",&x1,&y1,&x2,&y2,&x3,&y3,&x4,&y4);ss[m++] = Seg(x1,x2,y1,1);ss[m++] = Seg(x3,x4,y3,-1);ss[m++] = Seg(x3,x4,y4,1);ss[m++] = Seg(x1,x2,y2,-1);}sort(ss,ss + m);unsigned int ans = 0;for(int i = 0; i < m - 1; ++i){update(ss[i].l,ss[i].r - 1,ss[i].v,0,50000,1);ans += length[1] * (ss[i+1].y - ss[i].y);}cout<<ans<<endl;}}
