#include "railroad.h"
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
ll plan_roller_coaster(vector<int> s,vector<int> t){
int n=s.size();
vector<int> a;
for(int i=0;i<n;i++){
a.emplace_back(s[i]);
a.emplace_back(t[i]);
}
sort(a.begin(),a.end());
a.erase(unique(a.begin(),a.end()),a.end());
int m=a.size();
for(auto &x:s)x=lower_bound(a.begin(),a.end(),x)-a.begin();
for(auto &x:t)x=lower_bound(a.begin(),a.end(),x)-a.begin();
vector<int> b(m),p(m);
iota(p.begin(),p.end(),0);
function<int(int)> fp=[&](int u){
return p[u]=u==p[u]?u:fp(p[u]);
};
auto uni=[&](int u,int v){
p[fp(u)]=fp(v);
};
for(int i=0;i<n;i++){
b[s[i]]++,b[t[i]]--;
uni(s[i],t[i]);
}
ll ans=0;
for(int i=0;i<m-1;i++){
b[i+1]+=b[i];
ans+=1LL*max(0,b[i])*(a[i+1]-a[i]);
if(a[i]!=1)uni(i,i+1);
else if(fp(i)!=fp(i+1))uni(i,i+1),ans+=a[i+1]-a[i];
}
return ans;
}
