#include <bits/stdc++.h>
#include "railroad.h"
using namespace std;
class dsu {
public:
vector<int> p;
int n;
dsu(int n): n(n) {
p.resize(n);
for (int i = 0; i < n; ++i) {
p[i] = i;
}
}
inline int find(int x) {
while (x != p[x]) {
x = p[x] = p[p[x]];
}
return x;
}
inline bool unite(int x, int y) {
x = find(x);
y = find(y);
if (x == y) {
return false;
} else {
p[x] = y;
return true;
}
}
};
long long plan_roller_coaster(vector<int> s, vector<int> t) {
int n = s.size();
vector<int> disc;
for (int i = 0; i < n; ++i) {
disc.push_back(s[i]);
disc.push_back(t[i]);
}
sort(disc.begin(), disc.end());
disc.erase(unique(disc.begin(), disc.end()), disc.end());
int m = disc.size();
dsu d(m);
vector<int> pass_by(m);
for (int i = 0; i < n; ++i) {
s[i] = lower_bound(disc.begin(), disc.end(), s[i]) - disc.begin();
t[i] = lower_bound(disc.begin(), disc.end(), t[i]) - disc.begin();
++pass_by[s[i]];
--pass_by[t[i]];
d.unite(s[i], t[i]);
}
long long ans = 0;
vector<pair<int, int>> edges;
for (int i = 0; i < m - 1; ++i) {
pass_by[i + 1] += pass_by[i];
if (pass_by[i] > 1) {
ans += (long long) (disc[i + 1] - disc[i]) * (pass_by[i] - 1);
}
if (pass_by[i] == 1) {
edges.emplace_back(disc[i + 1] - disc[i], i);
} else {
d.unite(i, i + 1);
}
}
sort(edges.begin(), edges.end());
for (auto p : edges) {
if (d.unite(p.second, p.second + 1)) {
ans += p.first;
}
}
return ans;
}
