#include<bits/stdc++.h>
typedef long long ll;
#define pb push_back
#define fr first
#define sc second
#define endl '\n'
using namespace std;
#define mid ((left+right)>>1)
struct Seg{
int n,k;
vector<int>sum,pre,loc;
void build(int node=1,int left=0,int right=-1){
if(right==-1)right=n-1;
if(left==right){
pre[node]=sum[node]=k;
loc[node]=left;
return;
}
build(node*2,left,mid);
build(node*2+1,mid+1,right);
sum[node]=sum[node*2]+sum[node*2+1];
if(pre[node*2]>=0||pre[node*2]>pre[node*2+1]+sum[node*2]){
loc[node]=loc[node*2];
pre[node]=pre[node*2];
}
else{
loc[node]=loc[node*2+1];
pre[node]=pre[node*2+1]+sum[node*2];
}
}
void init(int N,int K){
n=N;
k=K;
sum.resize(n<<2);
pre.resize(n<<2);
loc.resize(n<<2);
build();
}
int l,r;
void up(int node=1,int left=0,int right=-1){
if(right==-1)right=n-1;
if(left==right){
sum[node]+=r;
pre[node]=sum[node];
return;
}
if(l>mid)up(node*2+1,mid+1,right);
else up(node*2,left,mid);
sum[node]=sum[node*2]+sum[node*2+1];
if(pre[node*2]>=0||pre[node*2]>pre[node*2+1]+sum[node*2]){
loc[node]=loc[node*2];
pre[node]=pre[node*2];
}
else{
loc[node]=loc[node*2+1];
pre[node]=pre[node*2+1]+sum[node*2];
}
}
void update(int tar,int val){
l=tar;r=val;
up();
}
pair<int,pair<int,int>> qu(int node=1,int left=0,int right=-1){
if(right==-1)right=n-1;
if(left>=l&&right<=r)return pair<int,pair<int,int>>{loc[node],{sum[node],pre[node]}};
if(left>r||right<l)return pair<int,pair<int,int>>{-1,{0,-1e9}};
pair<int,pair<int,int>>res,res1=qu(node*2,left,mid),res2=qu(node*2+1,mid+1,right);
res.sc.fr=res1.sc.fr+res2.sc.fr;
if(res1.sc.sc>=0||res1.sc.sc>res2.sc.sc+res1.sc.fr){
res.fr=res1.fr;
res.sc.sc=res1.sc.sc;
}
else{
res.fr=res2.fr;
res.sc.sc=res2.sc.sc+res1.sc.fr;
}
return res;
}
pair<int,pair<int,int>> query(int left,int right){
l=left;r=right;
return qu();
}
};
int n;
int arr[100023][2];
ll ans=0;
Seg seg,seg2;
void ekle(int from,int tar,int k,int x){
if(x==0)return;
arr[tar][k]+=x;
arr[from][k]-=x;
ans+=x;
if(k==0){
seg2.update(tar,x);
seg2.update(from,-x);
}
seg.update(tar,x);
seg.update(from,-x);
}
void f(int left,int right){
if(left==right){
if(arr[left][0]!=1)ans++;
return;
}
pair<int,pair<int,int>> k=seg.query(left,right);
int mi=k.fr;
//cout<<left<<" "<<mi<<" "<<right<<endl;
if(mi==right){
int a=arr[mi][0],b=arr[mi][1];
ekle(mi,mi-1,0,max(0,arr[mi][0]-1-!b));
ekle(mi,mi-1,1,max(0,arr[mi][1]-1-!a));
/*for(int j=0;j<2;j++){
for(int i=0;i<n;i++){
cout<<arr[i][j]<<" ";
}
cout<<endl;
}
cout<<endl;*/
f(mi,mi);
f(left,mi-1);
return;
}
int s=k.sc.fr+2*(right-left+1),a=k.sc.sc+2*(mi-left+1),b=s-a;
int ust=seg2.query(left,mi).sc.fr,alt=a-ust;
int need=k.sc.sc;
//cout<<need<<endl;
if(need<=min(arr[mi][0],ust-alt)){
ekle(mi,mi+1,0,need);
}
else if(need<=min(arr[mi][1],alt-ust)){
ekle(mi,mi+1,1,need);
}
else{
if(ust>alt){
int x=min(arr[mi][0],ust-alt);
ekle(mi,mi+1,0,x);
need-=x;
ust-=x;
}
else{
int x=min(arr[mi][1],alt-ust);
ekle(mi,mi+1,1,x);
need-=x;
alt-=x;
}
int x=min(min(arr[mi][0],arr[mi][1]),need/2);
ekle(mi,mi+1,0,x);
ekle(mi,mi+1,1,x);
need-=x*2;
if(need){
if(arr[mi][0]){
ekle(mi,mi+1,0,need);
}
else{
ekle(mi,mi+1,1,need);
}
}
}
/*for(int j=0;j<2;j++){
for(int i=0;i<n;i++){
cout<<arr[i][j]<<" ";
}
cout<<endl;
}
cout<<endl;*/
f(left,mi);
f(mi+1,right);
}
int main(){
ios_base::sync_with_stdio(23^23);cin.tie(NULL);
cin>>n;
seg.init(n,-2);
seg2.init(n,0);
for(int i=1;i<=2*n;i++){
pair<int,int>p;cin>>p.fr>>p.sc;
if(p.fr<1){
ans+=1-p.fr;
p.fr=1;
}
if(p.fr>n){
ans+=p.fr-n;
p.fr=n;
}
if(p.sc<1){
ans+=1-p.sc;
p.sc=1;
}
if(p.sc>2){
ans+=p.sc-2;
p.sc=2;
}
arr[p.fr-1][p.sc-1]++;
seg.update(p.fr-1,1);
if(p.sc-1==0){
seg2.update(p.fr-1,1);
}
}
/*cout<<ans<<endl;
for(int j=0;j<2;j++){
for(int i=0;i<n;i++){
cout<<arr[i][j]<<" ";
}
cout<<endl;
}*/
f(0,n-1);
cout<<ans<<endl;
}
