#include<bits/stdc++.h>
typedef long long ll;
#define pb push_back
#define fr first
#define sc second
#define endl '\n'
using namespace std;
struct Fen{
int n;
vector<int>tree;
void init(int N){
n=N;
tree.resize(n+1,0);
}
void update(int tar,int x){
while(tar<=n){
tree[tar]+=x;
tar+=(tar&-tar);
}
}
int qu(int tar){
int res=0;
while(tar>0){
res+=tree[tar];
tar-=(tar&-tar);
}
return res;
}
int query(int left,int right){
if(left>right)return 0;
return qu(right)-qu(left-1);
}
};
int n;
int arr[100023][2];
ll ans=0;
set<int>st;
Fen fen,fen2;
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){
fen2.update(tar,x);
fen2.update(from,-x);
}
fen.update(tar,x);
fen.update(from,-x);
}
void f(int left,int right){
if(left==right){
if(arr[left][0]!=1)ans++;
return;
}
int mi=-1;
if(arr[left][0]+arr[left][1]>=2)mi=left;
else{
int x=left;
while(true){
x=*st.upper_bound(x);
if(x>right)break;
if(fen.query(left,x)<2*(x-left+1)){
st.erase(x);
continue;
}
mi=x;
break;
}
}
//cout<<left<<" "<<mi<<" "<<right<<endl;
if(mi==-1||mi==right){
mi=right;
int a=arr[mi][0],b=arr[mi][1];
ekle(mi,mi-1,0,max(0,a-1-!b));
ekle(mi,mi-1,1,max(0,b-1-!a));
/*for(int j=0;j<2;j++){
for(int i=1;i<=n;i++){
cout<<arr[i][j]<<" ";
}
cout<<endl;
}
cout<<endl;*/
f(mi,mi);
f(left,mi-1);
return;
}
int s=fen.query(left,right),a=fen.query(left,mi),b=s-a;
int ust=fen2.query(left,mi),alt=a-ust;
int need=a-2*(mi-left+1);
assert(need>=0);
//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=1;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;
fen.init(n);
fen2.init(n);
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][p.sc-1]++;
fen.update(p.fr,1);
if(p.sc-1==0){
fen2.update(p.fr,1);
}
}
int sum=0;
st.insert(n+1);
for(int i=1;i<=n;i++){
sum+=arr[i][0]+arr[i][1];
if(sum>=2*i)st.insert(i);
}
/*cout<<ans<<endl;
for(int j=0;j<2;j++){
for(int i=1;i<=n;i++){
cout<<arr[i][j]<<" ";
}
cout<<endl;
}*/
f(1,n);
cout<<ans<<endl;
}
