#include <cstdio>
#include <stdio.h>
#include <stdbool.h>
#include <iostream>
#include <map>
#include <vector>
#include <climits>
#include <stack>
#include <string>
#include <queue>
#include <algorithm>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <cmath>
#include <cctype>
#include <bitset>
#include <iomanip>
#include <cstring>
#include <numeric>
#include <cassert>
using namespace std;
#define int long long
#define pii pair<int, int>
#define mp make_pair
#define pb push_back
#define fi first
#define se second
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n;
cin>>n;
deque<pii> top, down;
for (int i=0, a, b; i<2*n; ++i){
cin>>a>>b;
if (b>=2)down.pb(mp(a, b));
else top.pb(mp(a, b));
}
sort(top.begin(), top.end());
sort(down.begin(), down.end());
top.push_front(mp(0, 0));
down.push_front(mp(0, 0));
vector<vector<int> > dp(top.size(), vector<int>(down.size(), LLONG_MAX/2));
dp[0][0]=0;
for (int i=0; i<top.size(); ++i){
for (int j=0; j<down.size(); ++j){
if (i>=1&&j>=1)dp[i][j]=min(dp[i][j], dp[i-1][j-1]+abs(top[i].se-1)+abs(top[i].fi-((i+j)/2))+abs(down[j].se-2)+abs(down[j].fi-((i+j)/2)));
if (j>=2)dp[i][j]=min(dp[i][j], dp[i][j-2]+abs(down[j-1].se-1)+abs(down[j-1].fi-((i+j)/2))+abs(down[j].se-2)+abs(down[j].fi-((i+j)/2)));
if (i>=2)dp[i][j]=min(dp[i][j], dp[i-2][j]+abs(top[i-1].se-1)+abs(top[i-1].fi-((i+j)/2))+abs(top[i].se-2)+abs(top[i].fi-((i+j)/2)));
}
}
cout<<dp[top.size()-1][down.size()-1];
}
