#include "railroad.h"
#ifndef EVAL
#include "grader.cpp"
#endif
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define pii pair<int,int>
const int MAXN = 4e5+5;
ll inf = 1e18;
int n;
vector<int> s, t;
int pos_all[MAXN];
vector<int> edges[MAXN], rev[MAXN];
vector<pii> all;
bool used[MAXN];
void dfs(int u){
used[u] = true;
for(auto v : edges[u]){
if(!used[v])dfs(v);
}
}
void dfs_rev(int u){
used[u] = true;
for(auto v : rev[u]){
if(!used[v])dfs_rev(v);
}
}
ll plan_roller_coaster(vector<int> sk, vector<int> tk) {
s = sk, t = tk;
n = s.size();
for(int i=0;i<n;i++){
all.push_back({s[i], i});
all.push_back({t[i], i+n});
pos_all[i] = s[i];
pos_all[i+n] = t[i];
edges[i].push_back(i+n);
rev[i+n].push_back(i);
}
sort(all.begin(), all.end());
auto [no_need_1, fff] = all[0];
auto [no_need_2, sss] = all[(int)all.size()-1];
edges[sss].push_back(fff);
rev[fff].push_back(sss);
{ /// Making A = B
multiset<int> getting, bgetting;
int A=0, B=0;
for(int i=0;i<(int)all.size()-1;i++){
int ind1 = all[i].second;
int ind2 = all[i+1].second;
for(auto x : edges[ind1]){
if(getting.count(x)){
getting.erase(getting.find(x));
B--;
}else {
if(pos_all[ind1] <= pos_all[x]){
A++;
bgetting.insert(ind1);
}else assert(false);
}
}
for(auto x : rev[ind1]){
if(bgetting.count(x)){
bgetting.erase(bgetting.find(x));
A--;
}else {
if(pos_all[ind1] <= pos_all[x]){
B++;
getting.insert(ind1);
}else assert(false);
}
}
//~ cout << A << '-' << B << '\n';
if(A > B)return 1000000000;
if(A < B){
A++;
edges[ind1].push_back(ind2);
rev[ind2].push_back(ind1);
bgetting.insert(ind1);
}
}
}
/// check for connectivity
memset(used, 0, sizeof used);
dfs(0);
for(int i=0;i<n*2;i++){
if(!used[i])return 987654321;
}
memset(used, 0, sizeof used);
dfs_rev(0);
for(int i=0;i<n*2;i++){
if(!used[i])return 123456789;
}
/// now we need to start from arbitrary node and check for eulerian circuit
int now = 0;
while(!edges[now].empty()){
int t = edges[now].back();
edges[now].pop_back();
now = t;
}
for(int i=0;i<n*2;i++){
if(!edges[i].empty())return 999999999;
}
return 0;
}
