#include<bits/stdc++.h>
using namespace std;
struct node{
    int lx,rx; 
    int ly,ry; 
}a[5001];
int n,nl[20005]; 
bool cmp1(node x,node y){ 
	return x.lx<y.lx; 
}
bool cmp2(node x,node y){ 
	return x.ly<y.ly; 
}
void hs(int x){
	a[x].lx+=10001; 
	a[x].ly+=10001; 
	a[x].rx+=10001; 
	a[x].ry+=10001;
	return;
}
int main(){
	freopen("picture.in","r",stdin);
	freopen("picture.out","w",stdout);
	std::cin>>n;
    for(int i=1;i<=n;i++){
        std::cin>>a[i].lx>>a[i].ly>>a[i].rx>>a[i].ry;
        hs(i);
    }
	memset(nl,-1,sizeof(nl));
    int ans1=0,ans2=0;
    sort(a+1,a+1+n,cmp1);
    for(int i=1;i<=n;i++){
        for(int j=a[i].ly;j<a[i].ry;j++){
            if(nl[j]<a[i].lx) ans1+=2;
            if(nl[j]<a[i].rx) nl[j]=a[i].rx;
        }
    }
    memset(nl,-1,sizeof(nl));
    sort(a+1,a+1+n,cmp2);
    for(int i=1;i<=n;i++){
        for(int j=a[i].lx;j<a[i].rx;j++){
            if(nl[j]<a[i].ly) ans2+=2;
            if(nl[j]<a[i].ry) nl[j]=a[i].ry;
        }
    }
    std::cout<<ans1+ans2<<endl;
    return 0;
}