#include<cstdio>
#include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;
typedef long long ll;
const int N=1e5+5;
int read()
{int x=0,f=1;char ch=getchar();while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}return x*f;
}
struct block
{int x,y,xx,yy;
}s[N];
int cmp2 (block a,block b)
{//if(a.x==b.x)return a.xx<b.xx;return a.x<b.x;
}
int abss(int val)
{return val>=0?val:-val;
}
int n;
ll ans;
int main()
{n=read();for(int i=1;i<=n;i++)s[i].x=read(),s[i].y=read(),s[i].xx=read(),s[i].yy=read(),ans+=2LL*(s[i].xx-s[i].x)*(s[i].yy-s[i].y);
//    cout<<ans<<endl;sort(s+1,s+n+1,cmp2);for(int i=1;i<=n;i++){for(int j=i+1;j<=n;j++){if(s[j].x>s[i].xx+1)break;    if(((s[j].xx+1==s[i].x)||(s[j].x-1==s[i].xx))&&((s[j].y-1==s[i].yy)||(s[j].yy+1==s[i].y)))ans++;else if(s[j].xx+1==s[i].x||s[j].x-1==s[i].xx){if(s[j].yy<=s[i].yy&&s[j].y>=s[i].y){ans+=2LL*(s[j].yy-s[j].y);if(s[i].yy>s[j].yy)ans++;if(s[i].y<s[j].y)ans++;}else if(s[j].yy>s[i].yy&&s[j].y<s[i].y){ans+=2LL*(s[i].yy-s[i].y)+2;}else if(s[j].y>=s[i].y&&s[j].y<=s[i].yy){ans+=2LL*(s[i].yy-s[j].y);if(s[j].yy>s[i].yy)ans++;if(s[j].y>s[i].y)ans++;}else if(s[j].yy>=s[i].y&&s[j].yy<=s[i].yy){ans+=2LL*(s[j].yy-s[i].y);if(s[j].yy<s[i].yy)ans++;if(s[j].y<s[i].y)ans++;}}else if(s[j].y==s[i].yy+1||s[j].yy+1==s[i].y){if(s[i].x<=s[j].x&&s[i].xx>=s[j].xx){ans+=2LL*(s[j].xx-s[j].x);if(s[j].x>s[i].x)ans++;if(s[j].xx<s[i].xx)ans++;}else if(s[i].x>s[j].x&&s[i].xx<s[j].xx){ans+=2LL*(s[i].xx-s[i].x)+2;}else if(s[j].x>=s[i].x&&s[j].x<=s[i].xx){ans+=2LL*(s[i].xx-s[j].x);if(s[j].x>s[i].x)ans++;if(s[j].xx>s[i].xx)ans++;}else if(s[j].xx>=s[i].x&&s[j].xx<=s[i].xx){ans+=2LL*(s[j].xx-s[i].x);if(s[j].x<s[i].x)ans++;if(s[j].xx>s[i].xx)ans++;}}}}cout<<ans<<endl;return 0;
}