#include "railroad.h"
//Challenge: Accepted
#include <bits/stdc++.h>
using namespace std;
#ifdef zisk
void debug(){cout << endl;}
template<class T, class ... U> void debug(T a, U ... b){cout << a << " ", debug(b...);}
template<class T> void pary(T l, T r){
while (l != r) cout << *l << " ", l++;
cout << endl;
}
#else
#define debug(...) 0
#define pary(...) 0
#endif
#define ll long long
#define maxn 400005
#define pii pair<int, int>
#define ff first
#define ss second
const ll inf = 1LL<<60;
struct DSU{
int par[maxn];
void init(int n){
for (int i = 0;i <= n;i++) par[i] = i;
}
int find(int a){
return a == par[a] ? a : (par[a] = find(par[a]));
}
bool Union(int a, int b){
a = find(a), b = find(b);
if (a == b) return 0;
par[a] = b;
return 1;
}
} dsu;
struct obj{
int pos, val, id;
obj(){pos = val = id = 0;}
obj(int a, int b, int c){pos = a, val = b, id = c;}
};
int vis[maxn];
long long plan_roller_coaster(std::vector<int> S, std::vector<int> T) {
int n = (int) S.size();
vector<obj> a, ed;
for (int i = 0;i < n;i++) {
a.push_back(obj(S[i], 1, i));
a.push_back(obj(T[i], -1, i));
}
a.push_back(obj(1<<30, 1, n));
a.push_back(obj(1, -1, n));
sort(a.begin(),a.end(), [&] (obj x, obj y){return x.pos < y.pos;});
int siz = 2*n + 2;
dsu.init(siz);
ll cur = 0, x = 1;
ll ans = 0;
int ind = 0;
for (auto [pos, val, id]:a) {
if (cur != 0) {
ans += max(cur, 0LL) * (pos - x);
dsu.Union(ind, ind-1);
} else if (ind){
ed.push_back(obj(ind, ind-1, pos - x));
}
x = pos;
cur += val;
if (vis[id]) {
dsu.Union(ind, vis[id]-1);
} else {
vis[id] = ind+1;
}
ind++;
}
debug(ans);
sort(ed.begin(), ed.end(), [&] (obj x, obj y){return x.id < y.id;});
for (auto [u, v, w]:ed) {
if (dsu.Union(u, v)) ans += w;
}
return ans;
}
