import java.util.*;
class Coin implements Comparable<Coin> {
int X, Y;
public Coin(int X, int Y) {
this.X = X;
this.Y = Y;
}
public int compareTo(Coin other) {
return Integer.compare(this.X, other.X);
}
}
public class joi2019_ho_t4 {
static final long INF = Long.MAX_VALUE / 2;
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int N = sc.nextInt();
int total = 2 * N;
Coin[] coins = new Coin[total];
for (int i = 0; i < total; i++) {
int X = sc.nextInt();
int Y = sc.nextInt();
coins[i] = new Coin(X, Y);
}
Arrays.sort(coins);
long costoHorizontal = 0;
for (int i = 0; i < total; i++) {
int destinoX = (i / 2) + 1;
costoHorizontal += Math.abs(coins[i].X - destinoX);
}
long[][] dp = new long[total + 1][N + 1];
for (int i = 0; i <= total; i++) {
Arrays.fill(dp[i], INF);
}
dp[0][0] = 0;
for (int i = 1; i <= total; i++) {
for (int j = Math.max(0, i - N); j <= Math.min(i, N); j++) {
if (j > 0) {
dp[i][j] = Math.min(dp[i][j], dp[i-1][j-1] + Math.abs(coins[i-1].Y - 1));
}
if ((i - j) > 0 && (i - j) <= N) {
dp[i][j] = Math.min(dp[i][j], dp[i-1][j] + Math.abs(coins[i-1].Y - 2));
}
}
}
long costoVertical = dp[total][N];
long respuestaTotal = costoHorizontal + costoVertical;
System.out.println(respuestaTotal);
}
}
