#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
#define all(x) x.begin(), x.end()
template <typename T1, typename T2> inline void chkmin(T1 &x, const T2 & y) {if (x > y) x = y;}
template <typename T1, typename T2> inline void chkmax(T1 &x, const T2 & y) {if (x < y) x = y;}
#define int ll
const int MAXN = 2e5 + 10;
int n;
int c[MAXN][2];
ll ans;
void make(int & a, int l, int r) {
if (a < l) ans += l - a, a = l;
if (a > r) ans += a - r, a = r;
}
void read() {
cin >> n;
for (int i = 0; i < 2 * n; i++) {
int x, y;
cin >> x >> y;
make(x, 1, n);
make(y, 1, 2);
x--;
y--;
c[x][y]++;
}
}
void run() {
for (int i = 0; i < n; i++) {
int t0 = c[i][0];
int t1 = c[i][1];
t0--;
t1--;
if (t0 * t1 < 0) {
int t = min(abs(t0), abs(t1));
if (t0 < 0) t0 += t, t1 -= t;
else t0 -= t, t1 += t;
ans += t;
}
ans += abs(t0) + abs(t1);
c[i + 1][0] += t0;
c[i + 1][1] += t1;
}
}
void write() {
cout << ans << endl;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
read();
run();
write();
return 0;
}
