/* Author : Mychecksdead */
#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define MOD (1000000000+7)
#define MOD1 (998244353)
#define pb push_back
#define all(x) x.begin(), x.end()
#define en cout << '\n'
#define ff first
#define ss second
#define pii pair<int,int>
#define vi vector<int>
const int N = 1500+100, M = 1e5+10, K = 52, MX = 30;
const ll INF = 1e18;
int n;
ll dp[N][N];
array<ll, 2> a[N];
void assertt(bool x){
if(!x){
vi v;
for(int i = 0; i < MOD*2; ++i) v.pb(i);
}
}
void solve(){
cin >> n;
ll ans = 0;
vector<array<int, 2>> pt(n + 1);
for(int i = 1; i <= 2*n; ++i){
cin >> a[i][0] >> a[i][1];
if(a[i][0] < 1){
ans += 1 - a[i][0];
a[i][0] = 1;
}
if(a[i][0] > n){
ans += a[i][0] - n;
a[i][0] = n;
}
if(a[i][1] < 1){
ans += 1 - a[i][1];
a[i][1] = 1;
}
if(a[i][1] > 2){
ans += a[i][1] - 2;
a[i][1] = 2;
}
pt[a[i][0]][a[i][1] - 1]++;
// cerr << a[i][0] << ' ' << a[i][1] << '\n';
}
for(int i = 0; i <= n; ++i){
for(int j = 0; j <= n + 1; ++j) dp[i][j] = INF;
}
dp[0][0] = 0;
int cnt = 0;
for(int i = 1; i <= n; ++i){
for(int j = 0; j <= n; ++j) dp[i][j] = dp[i - 1][j];
int x = pt[i][1];
int y = pt[i][0];
vector<int> C;
if(x <= y){
for(int j = 0; j < x; ++j){
C.pb(1);
C.pb(0);
}
for(int j = 0; j < y - x; ++j) C.pb(1);
}else{
for(int j = 0; j < y; ++j){
C.pb(0);
C.pb(1);
}
for(int j = 0; j < x - y; ++j) C.pb(0);
}
for(int k = 1; k <= x + y; ++k){
int old_down = max(0, cnt / 2 - 5);
int old_up = min(n, cnt / 2 + 5);
++cnt;
int down = max(0, cnt/2 - 5);
int up = min(n, cnt/2 + 5);
int tp = C.back();
C.pop_back();
for(int j = up; j >= down; --j){
int cost1 = (!tp ? 1 : 0) + abs(i - (cnt - j)); // moving to down
int cost2 = (tp ? 1 : 0) + abs(i - j); // moving to down
if(j > old_down && j <= old_up) dp[i][j] = min(dp[i][j] + cost1, dp[i][j - 1] + cost2);
else if(j == old_down) dp[i][j] = dp[i][j] + cost1;
else dp[i][j] = dp[i][j - 1] + cost2;
}
}
// for(int j = 0; j <= n; ++j){
// cerr << i << ' ' << j << ' ' << cnt/2 << ' ' << dp[i][j] << '\n';
// }
// en;
// int mn = *min_element(dp[i], dp[i]+n+1);
// bool ok = false;
// for(int j = max(0, cnt/2 - 2); j <= min(n, cnt/2 + 2); ++j){
// if(mn == dp[i][j]) ok = 1;
// }
// assertt(ok);
}
cout << ans + dp[n][n];
}
int main(){
cin.tie(0); ios::sync_with_stdio(0);
int tt = 1, aa;
// freopen("in.txt", "r", stdin);
// freopen("out.txt", "w", stdout);
while(tt--){
solve();
en;
}
cerr<<"time taken : "<<(float)clock()/CLOCKS_PER_SEC<<" seconds\n";
return 0;
}
