#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
#define REP(i,n) for(int i=0;i<n;++i)
#define REP1(i,n) for(int i=1;i<=n;++i)
#define SZ(i) int(i.size())
#define eb emplace_back
#define ALL(i) i.begin(),i.end()
#define X first
#define Y second
#ifdef tmd
#define IOS()
#define debug(...) fprintf(stderr,"#%d: %s = ",__LINE__,#__VA_ARGS__),_do(__VA_ARGS__);
template<typename T> void _do(T &&x){cerr<<x<<endl;}
template<typename T, typename ...S> void _do(T &&x, S &&...y){cerr<<x<<", ";_do(y...);}
template<typename It> ostream& _printRng(ostream &os,It bg,It ed)
{
os<<"{";
for(It it=bg;it!=ed;it++) {
os<<(it==bg?"":",")<<*it;
}
os<<"}";
return os;
}
template<typename T> ostream &operator << (ostream &os,vector<T> &v){return _printRng(os,v.begin(), v.end());}
template<typename T> void pary(T bg, T ed){_printRng(cerr,bg,ed);cerr<<endl;}
#else
#define IOS() ios_base::sync_with_stdio(0);cin.tie(0);
#define endl '\n'
#define debug(...)
#define pary(...)
#endif
const int MAXN = 1003;
const ll MOD = 1000000007;
int n;
vector<pll> pos;
void solve (vector<int> x, ll &res) {
sort(ALL(x));
for (int i=1; i<=n; i++) {
res += abs(x[i-1] - i);
}
}
ll dp[MAXN*2][MAXN];
void ckmin (ll &x, ll y) {
x = x > y ? y : x;
}
/*********************GoodLuck***********************/
int main () {
IOS();
cin >> n;
REP (i, n*2) {
int x, y;
cin >> x >> y;
pos.eb(x, y);
}
sort(ALL(pos));
memset(dp, 0x3f, sizeof(dp));
dp[0][0] = 0;
for (int i=1; i<=n*2; i++) {
for (int u=0; u<=min(i,n); u++) {
int d = i-u;
if (d < 0 || d > n) {
continue;
}
if (d > 0) {
ckmin(dp[i][u],dp[i-1][u] + abs(pos[i-1].X - d) + abs(pos[i-1].Y - 1));
}
if (u > 0) {
ckmin(dp[i][u],dp[i-1][u-1] + abs(pos[i-1].X - u) + abs(pos[i-1].Y - 2));
}
debug(i, u, d, dp[i][u]);
}
}
cout << dp[n*2][n] << endl;
}
