1 #include<algorithm>
  2 #include<iostream>
  3 #include<cstdlib>
  4 #include<cstring>
  5 #include<cstdio>
  6 #include<cmath>
  7 #define MAXN 100010
  8 #define LL long long
  9 #define int LL
 10 #define max(a,b) ((a)>(b)?(a):(b))
 11 #define ma(x,y) memset(x,y,sizeof(x))
 12 using namespace std;
 13 int n,maxn,maxy;
 14 int map[1010][1010];
 15 struct ques
 16 {
 17     int x1,x2,ty1,ty2;
 18     #define x1(i) que[i].x1
 19     #define x2(i) que[i].x2
 20     #define ty1(i) que[i].ty1
 21     #define ty2(i) que[i].ty2
 22     friend bool operator < (ques a,ques b)
 23     {
 24         return a.x1==b.x1?a.ty1<b.ty1:a.x1<b.x1;
 25     }
 26 }que[MAXN];
 27 inline int read();
 28 void QJ2();
 29 signed main()
 30 {
 31     n=read();
 32     for(int i=1;i<=n;i++)
 33         x1(i)=read(),ty1(i)=read(),x2(i)=read(),ty2(i)=read();
 34     QJ2();
 35 }
 36 inline int read()
 37 {
 38     int s=0;char a=getchar();
 39     while(a<'0'||a>'9')a=getchar();
 40     while(a>='0'&&a<='9'){s=s*10+a-'0';a=getchar();}
 41     return s;
 42 }
 43 void QJ2()
 44 {
 45     sort(que+1,que+n+1);
 46     LL ans=0;
 47     for(int i=1;i<=n;i++)
 48         ans+=1ll*abs(x1(i)-x2(i))*abs(ty1(i)-ty2(i))*2;
 49     for(int i=1;i<=n;i++)
 50     for(int j=i+1;j<=n;j++)
 51     {
 52         if(i!=j)
 53         {
 54             if(ty1(j)==ty2(i)+1)//j上
 55             {
 56                 int ttt=min(x2(j),x2(i))-max(x1(j),x1(i))+1;
 57                 if(ttt>0)
 58                 {
 59                     ans+=(ttt-1)*2;
 60                     if(abs(x1(i)-x1(j))>0)ans++;
 61                     if(abs(x2(i)-x2(j))>0)ans++;
 62                 }
 63                 else if(abs(x1(i)-x1(j))==1||abs(x2(i)-x2(j))==1)ans++;
 64             }
 65             else if(ty2(j)==ty1(i)-1)//j下
 66             {
 67                 int ttt=min(x2(j),x2(i))-max(x1(j),x1(i))+1;
 68                 if(ttt>0)
 69                 {
 70                     ans+=(ttt-1)*2;
 71                     if(abs(x1(i)-x1(j))>0)ans++;
 72                     if(abs(x2(i)-x2(j))>0)ans++;
 73                 }
 74                 else if(abs(x1(i)-x1(j))==1||abs(x2(i)-x2(j))==1)ans++;
 75             }
 76             else if(x2(j)==x1(i)-1)//j左
 77             {
 78                 int ttt=min(ty2(j),ty2(i))-max(ty1(j),ty1(i))+1;
 79                 if(ttt>0)
 80                 {
 81                     ans+=(ttt-1)*2;
 82                     if(abs(ty1(i)-ty1(j))>0)ans++;
 83                     if(abs(ty2(i)-ty2(j))>0)ans++;
 84                 }
 85             }
 86             else if(x1(j)==x2(i)+1)//j右
 87             {
 88                 int ttt=min(ty2(j),ty2(i))-max(ty1(j),ty1(i))+1;
 89                 if(ttt>0)
 90                 {
 91                     ans+=(ttt-1)*2;
 92                     if(abs(ty1(i)-ty1(j))>0)ans++;
 93                     if(abs(ty2(i)-ty2(j))>0)ans++;
 94                 }
 95             }
 96             else if(x1(j)>x2(i)&&ty1(j)>ty2(i))break;
 97         }
 98     }
 99     printf("%lld\n",ans);
100     exit(0);
101 }