#pragma GCC optimize("O3")
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define pb push_back
#define ff first
#define ss second
#define MOD 1000000009
#define INF 1000000019
#define INFL 1000000000000000099
ll n,q,s,t,a,b,c,d,ans,bst,k,e,m,pier,h,w,u;
ll l1[100007],l2[100007];
vector<ll>v,v2;
int main()
{
ios_base::sync_with_stdio(0);cin.tie(0);
cin>>n;
for(ll i=0;i<2*n;i++){
cin>>a>>b;
ans+=abs(a-min(n,max(1LL,a)));
if(b>1){
ans+=b-2;
v2.pb(min(n,max(1LL,a)));
l2[min(n,max(1LL,a))]++;
}
else{
ans-=b-1;
v.pb(min(n,max(1LL,a)));
l1[min(n,max(1LL,a))]++;
}
}
for(ll i=1;i<=n;i++){
// cout<<l1[i]<<" "<<l2[i]<<"\n";
}//cout<<"\n\n";
for(ll i=n;i>=1;i--){
l1[i]--;
l2[i]--;
// cout<<ans<<" "<<l1[i]<<" "<<l2[i]<<"\n";
if(l1[i]>0 && l2[i]<0){
ans+=min(l1[i],-l2[i]);
ll ak=min(l1[i],-l2[i]);
l2[i]+=min(l1[i],-l2[i]);
l1[i]-=ak;
}
if(l1[i]<0 && l2[i]>0){
ans+=min(-l1[i],l2[i]);
ll ak=min(-l1[i],l2[i]);
l1[i]+=min(-l1[i],l2[i]);
l2[i]-=ak;
}
if(l1[i]>0 || l2[i]>0){
l1[i-1]+=l1[i];
l2[i-1]+=l2[i];
ans+=l1[i]+l2[i];
}
else{
l1[i-1]+=l1[i];
l2[i-1]+=l2[i];
ans-=l1[i];
ans-=l2[i];
}
}
cout<<ans;
}
