#include <bits/stdc++.h>
using ll = long long;
#define int ll
using namespace std;
#define sz(x) (int)(x).size()
#define foru(i, l, r) for(int i = l; i <= r; i++)
#define ford(i, l, r) for(int i = l; i >= r; i--)
#define fi first
#define se second
#define mod 998244353
#define db(x) cerr << __LINE__ << " " << #x << " " << x << "\n"
using vi = vector<int>;
using pi = pair<int, int>;
const ll N = 200005;
const ll inf = 1e18;
int n;
vi adj[N];
int calc(vi v){
int res = 0;
if(sz(v) < 2) return 0;
foru(i, 0, sz(v) - 1){
int mn = inf;
if(i + 1 < sz(v)) mn = min(mn, v[i + 1] - v[i]);
if(i != 0) mn = min(mn, v[i] - v[i - 1]);
res += mn;
}
return res;
}
void solve(){
cin >> n;
foru(i, 0, n - 1){
int x, y; cin >> x >> y;
adj[y].push_back(x);
}
int res = 0;
foru(i, 1, n){
sort(adj[i].begin(), adj[i].end());
res += calc(adj[i]);
}
cout << res;
}
signed main(){
ios_base::sync_with_stdio(0); cin.tie(0);
int t = 1;
while(t--){
solve();
}
}
