#include "islands.h"
#include <cassert>
#include <fstream>
#include <cstdio>
#include <variant>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <unordered_set>
#include <algorithm>
#include <iostream>
using namespace std;
variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V) {
vector<queue<int>> tree(N);
for(int i = 0; i < M; i ++){
tree[U[i]].push(V[i]);
}
vector<int> path1, path2, vis(N, 0);
path1.push_back(0);
while(path1.size()){
vis[path1.back()] = true;
if(tree[path1.back()].size()){
int a = tree[path1.back()].front();
tree[path1.back()].pop();
path1.push_back(a);
if(vis[path1.back()])break;
}
else{
vis[path1.back()] = false;
path1.pop_back();
}
}
for(int i : path1){
path2.push_back(i);
vis[i] = false;
while(path2.size()){
if(tree[path2.back()].size()){
int a = tree[path2.back()].front();
tree[path2.back()].pop();
path2.push_back(a);
if(vis[path2.back()])break;
}
else{
path2.pop_back();
}
}
vis[i] = true;
if(path2.size())break;
}
for(int i : path2){
path1.push_back(i);
}
if(path1.size() && path2.size()){
return path1;
}
return false;
}
