/* 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 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];
    for(int k = 1; k <= x + y; ++k){
      ++cnt;
      for(int j = n; j >= 0; --j){               
        int cost1 = (k <= x ? 1 : 0) + abs(i - (cnt - j)); // moving to down
        int cost2 = (k > x ? 1 : 0) + abs(i - j); // moving to down
        if(j > 0) dp[i][j] = min(dp[i][j] + cost1, dp[i][j - 1] + cost2);
        else dp[i][j] = dp[i][j] + cost1;
      }
    }
    // for(int j = 0; j <= n; ++j){
    //   cerr << i  << ' ' << j << ' ' << dp[i][j] << '\n';
    // }
    // en;
  }
  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;
} 
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