#include<iostream>

 #include<cstring>

 #include<cstdio>

 #include<algorithm>

 using namespace std;

 const int maxn=;

 int num;

 struct Node{

     int  l;

     int  r;

     int tp;

     int  y;

  bool operator <(Node a) const{

             return y<a.y;

       }

 }line[*maxn];

 int  arr[*maxn];

 struct Edge{

     int left;

     int right;

     int flag;

     int  sum;

 }node1[maxn*];

 void build(int l,int r,int idx){

     node1[idx].left=l;

     node1[idx].right=r;

     if(l==r){

         node1[idx].flag=;

         node1[idx].sum=;

         return;

     }

     int mid=(l+r)/;

     build(l,mid,idx<<);

     build(mid+,r,idx<<|);

     node1[idx].sum=node1[idx<<].sum+node1[idx<<|].sum;

 }

 void update(int l,int r,int f,int idx){

     if(node1[idx].left==node1[idx].right){

           node1[idx].flag+=f;

         if(node1[idx].flag)node1[idx].sum=arr[node1[idx].right+]-arr[node1[idx].left];

         if(!node1[idx].flag)node1[idx].sum=;

         return ;

     }

     int mid=(node1[idx].left+node1[idx].right)/;

     if(mid>=r)update(l,r,f,idx<<);

     else if(mid<l)update(l,r,f,idx<<|);

     else{

         update(l,mid,f,idx<<);

         update(mid+,r,f,idx<<|);

     }

     node1[idx].sum=node1[idx<<].sum+node1[idx<<|].sum;

 }

 int binaryserach(int  x){

    int l,r,mid;

       l=,r=num+;

       while (r-l>){

             mid=(l+r)>>;

             if (arr[mid]<=x) l=mid;

                else r=mid;

       }

       return l;

 }

 int main(){

     int n;int  x1,y1,x2,y2;

     long long ans;

   while(~scanf("%d%d%d%d",&x1,&y1,&x2,&y2)){

       if(x1==-&&x2==-&&y1==-&&y2==-)break;

         num=;int cnt=;

         line[].l=x1;line[].r=x2;line[].y=y1;line[].tp=;

           line[].l=x1;line[].r=x2;line[].y=y2;line[].tp=-;

           arr[++num]=x1;arr[++num]=x2;

       while(~scanf("%d%d%d%d",&x1,&y1,&x2,&y2)){

           if(x1==-&&x2==-&&y1==-&&y2==-)break;

           line[++cnt].l=x1;line[cnt].r=x2;line[cnt].y=y1;line[cnt].tp=;

           line[++cnt].l=x1;line[cnt].r=x2;line[cnt].y=y2;line[cnt].tp=-;

           arr[++num]=x1;arr[++num]=x2;

       }

       sort(arr+,arr+num+);

         ans=;

       sort(line+,line+cnt+);

       build(,cnt,);

      for(int i=;i<=cnt;i++){

           ans+=node1[].sum*(line[i].y-line[i-].y);

           int l=binaryserach(line[i].l);

           int r=binaryserach(line[i].r)-;

            update(l,r,line[i].tp,);

       }

     printf("%I64d\n",ans);

   }

 }