#include "railroad.h"
#include "bits/stdc++.h"
using namespace std;
#define FAST ios_base::sync_with_stdio(false); cin.tie(0);
#define pb push_back
#define eb emplace_back
#define ins insert
#define f first
#define s second
#define cbr cerr<<"hi\n"
#define mmst(x, v) memset((x), v, sizeof ((x)))
#define siz(x) ll(x.size())
#define all(x) (x).begin(), (x).end()
#define lbd(x,y) (lower_bound(all(x),y)-x.begin())
#define ubd(x,y) (upper_bound(all(x),y)-x.begin())
// mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
// inline long long rand(long long x, long long y) { return rng() % (y+1-x) + x; } //inclusive
string inline to_string(char c) {string s(1,c);return s;} template<typename T> inline T gcd(T a,T b){ return a==0?llabs(b):gcd(b%a,a); }
using ll=long long;
using ld=long double;
#define FOR(i,s,e) for(ll i=s;i<=ll(e);++i)
#define DEC(i,s,e) for(ll i=s;i>=ll(e);--i)
using pi=pair<ll,ll>; using spi=pair<ll,pi>; using dpi=pair<pi,pi>;
long long LLINF = 1e18;
int INF = 1e9+1e6;
#define MAXN (200006)
int n;
vector<int> d, co, p;
void init() { FOR(i,0,siz(p)-1) p[i]=i; }
int find(int x) { return p[x] == x ? x : p[x] = find(p[x]); }
bool merge(int x,int y) { x=find(x), y=find(y); if(x==y) return 0; p[x] = y; return 1; }
long long plan_roller_coaster(vector<int> s, vector<int> t) {
s.eb(1e9), t.eb(1), n = siz(s);
FOR(i,0,n-1) {
d.eb(s[i]), d.eb(t[i]);
}
sort(all(d)), d.resize(unique(all(d))-d.begin());
co.resize(siz(d), 0), p.resize(siz(d), 0), init();
FOR(i,0,n-1) {
++ co[lbd(d, s[i])], -- co[lbd(d, t[i])];
merge(lbd(d, s[i]), lbd(d, t[i]));
}
ll ans = 0;
int cur = 0;
vector<spi> e;
DEC(i,siz(d)-1,1) {
cur += co[i];
if(cur < 0) {
ans += ll(d[i] - d[i-1]) * -cur;
merge(i, i-1);
} else if(cur > 0) {
merge(i, i-1);
} else {
e.eb(d[i]-d[i-1], pi(i, i-1));
}
}
sort(all(e));
for(auto i:e) {
int a = i.s.f, b = i.s.s;
if(merge(a, b)) ans += i.f;
}
return ans;
}
