#include<bits/stdc++.h>
using namespace std;
int haha[100001][2];
long long dp[3000][3000];
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
int n,x,y;
cin >> n;
long long ans = 0;
for(int i = 1; i <= n; i++) {
haha[i][0] = 0;
haha[i][1] = 0;
}
for(int i = 0; i < 2*n; i++) {
cin >> x >> y;
if(x < 1) {
ans+=1-x;
x = 1;
}
else if(x > n) {
ans+=x-n;
x = n;
}
if(y < 1) {
ans+=1-y;
y = 1;
}
else if(y > 2) {
ans+=y-2;
y = 2;
}
haha[x][y-1]++;
}
int sb = 0;
for(int i = 0; i <= 2*n; i++) {
dp[0][i] = INT_MAX/2;
}
dp[0][0] = 0;
for(int i = 1; i <= n; i++) {
int k = haha[i][0]+haha[i][1],a = haha[i][0];
sb+=k;
for(int j = 0; j <= 2*n; j++) {
dp[i][j] = INT_MAX/2;
}
for(int j = 0; j <= 2*n; j++) {
for(int y = 0; y <= k && j+y <= 2*n; y++) {
dp[i][j+y] = min(dp[i][j+y],dp[i-1][j]+abs(i-(j+y))+abs(i-(sb-(j+y)))+abs(y-a));
}
}
}
cout << ans+dp[n][n];
return 0;
}
