#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
class CoinCollector {
private:
int N;
vector<vector<ll>> dp;
vector<vector<ll>> coins;
ll processInitialPosition(ll x, ll y) {
ll moves = 0;
if (x < 1) {
moves += 1 - x;
x = 1;
} else if (x > N) {
moves += x - N;
x = N;
}
if (y < 1) {
moves += 1 - y;
y = 1;
} else if (y > 2) {
moves += y - 2;
y = 2;
}
coins[x][y-1]++;
return moves;
}
ll calculateMinimumMoves() {
dp.assign(N + 2, vector<ll>(N + 2, 0));
for (int len = 1; len <= N; len++) {
for (int i = 1; i + len - 1 <= N; i++) {
int j = i + len - 1;
ll up = 0, down = 0;
for (int k = i; k <= j; k++) {
up += coins[k][0] - 1;
down += coins[k][1] - 1;
}
if (len == 1) {
dp[i][j] = abs(up) + abs(down);
if (up > 0 && down < 0) {
dp[i][j] += min(up, -down);
} else if (up < 0 && down > 0) {
dp[i][j] += min(-up, down);
}
} else {
dp[i][j] = LLONG_MAX;
for (int k = i; k < j; k++) {
dp[i][j] = min(dp[i][j], dp[i][k] + dp[k+1][j] + len);
}
}
}
}
return dp[1][N];
}
public:
ll solve() {
cin >> N;
coins.assign(N + 1, vector<ll>(2, 0));
ll initial_moves = 0;
for (int i = 0; i < 2 * N; i++) {
ll x, y;
cin >> x >> y;
initial_moves += processInitialPosition(x, y);
}
return initial_moves + calculateMinimumMoves();
}
};
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
CoinCollector solver;
cout << solver.solve() << endl;
return 0;
}
