#include "islands.h"
#include <bits/stdc++.h>
#define N 100005
using namespace std;
vector<pair<int,pair<int,int>>> adj[N];
map<int,vector<int>> mp[N];
int par[N];
int par2[N];
int vis[N];
vector<int> ans = {};
bool ok = 0;
void dfs2(int v,int pr){
vis[v] = 1;
vector<pair<int,pair<int,int>>> tmp;
for(auto u:adj[v]){
if(ok)
return;
if(vis[u.first] == 2){
continue;
}
if(vis[u.first] == 1){
if(ok)
return;
ok = 1;
int now = u.first;
while(now != 0){
ans.push_back(par[now]);
now = par2[now];
}
reverse(ans.begin(),ans.end());
vector<int> v1 = {},v2 = {};
now = v;
int cnt = 0;
int sz = 1;
while(now != u.first){
assert(cnt++ <= 1000);
v1.push_back(par[now]);
v2.push_back(par[now] + 1);
sz++;
// cout << now << endl;
now = par2[now];
}
reverse(v1.begin(),v1.end());
reverse(v2.begin(),v2.end());
v1.push_back(u.second.first);
v2.push_back(u.second.first + 1);
for(int i = 0;i<sz;i++){
for(int j = sz-i;j<sz;j++){
ans.push_back(v1[j]);
}
for(int j = 0;j<sz-i;j++){
ans.push_back(v1[j]);
}
for(int j = sz-i;j<sz;j++){
ans.push_back(v2[j]);
}
for(int j = 0;j<sz-i;j++){
ans.push_back(v2[j]);
}
}
now = u.first;
while(now != 0){
ans.push_back(par[now]);
now = par2[now];
}
return;
}
par[u.first] = u.second.first;
par2[u.first] = v;
dfs2(u.first,u.second.first);
}
vis[v] = 2;
}
variant<bool, vector<int>> find_journey(int n, int m, vector<int> U, vector<int> V){
for(int i = 0;i<m;i+=2){
adj[U[i]].push_back({V[i],{i,i+1}});
// cout << U[i] << ' ' << V[i] << endl;
}
dfs2(0,-1);
if(!ok)
return false;
return ans;
}
