#include <bits/stdc++.h>
#include <variant>
#include "islands.h"
using namespace std;
typedef int ll;
void dfs(ll k, vector<vector<pair<ll, ll>>> &g, vector<bool> &used){
if(used[k]) return;
used[k]=true;
for(ll i=0; i<g[k].size(); i++){
dfs(g[k][i].first, g, used);
}
}
variant<bool, vector<int>> find_journey(int n, int m, vector<int> u, vector<int> v){
if(n==2){
ll a=-1, b=-1, c=-1;
for(ll i=0; i<m; i++){
if(u[i]==0){
if(a==-1) a=i;
else b=i;
}
else c=i;
}
if(b==-1 || c==-1) return false;
return vector<int>({a, c, b, a, c, b});
}
else if(m==n*(n-1)){
ll a=-1, b=-1, c=-1, d=-1, e=-1, f=-1;
for(ll i=0; i<m; i++){
if(u[i]==0 && v[i]==1) a=i;
if(u[i]==1 && v[i]==0) b=i;
if(u[i]==1 && v[i]==2) c=i;
if(u[i]==2 && v[i]==1) d=i;
if(u[i]==2 && v[i]==0) e=i;
if(u[i]==0 && v[i]==2) f=i;
}
return vector<int>({a, c, e, f, d, b, e, c, a, b, d, f});
}
else{
vector<vector<pair<ll, ll>>> g(n);
vector<ll> res, res1;
for(ll i=0; i<m; i++){
g[u[i]].push_back({v[i], i});
}
if(g[0].size()>=2){
ll a=g[0][0].second, b=g[0][1].second;
ll a1, b1;
if(a%2==0) a1=a+1;
else a1=a-1;
if(b%2==0) b1=b+1;
else b1=b-1;
return vector<int>({a, a1, b, b1, a1, a, b1, b});
}
else{
bool f=false;
vector<bool> used(n);
dfs(0, g, used);
for(ll i=0; i<n; i++){
if(used[i] && g[i].size()>=3) f=true;
}
if(!f) return false;
ll l=g[0][0].first, k=0;
res1.push_back(g[0][0].second);
res.push_back(g[0][0].second);
while(g[l].size()<3){
if(g[l][0].first==k){
res1.push_back(g[l][1].second);
res.push_back(g[l][1].second);
k=l;
l=g[l][1].first;
}
else{
res1.push_back(g[l][0].second);
res.push_back(g[l][0].second);
k=l;
l=g[l][0].first;
}
}
ll a=-1, b=-1;
for(ll i=0; i<3; i++){
if(g[l][i].first!=k){
if(a==-1) a=g[l][i].second;
else b=g[l][i].second;
}
}
ll a1, b1;
if(a%2==0) a1=a+1;
else a1=a-1;
if(b%2==0) b1=b+1;
else b1=b-1;
res.push_back(a);
res.push_back(a1);
res.push_back(b);
res.push_back(b1);
res.push_back(a1);
res.push_back(a);
res.push_back(b1);
res.push_back(b);
reverse(res1.begin(), res1.end());
for(ll asdf:res1) res.push_back(asdf);
return res;
}
}
}
//~ int main(){
//~ int n, m;
//~ cin>>n>>m;
//~ vector<ll> u(m), v(m);
//~ for(ll i=0; i<m; i++){
//~ cin>>u[i]>>v[i];
//~ }
//~ vector<ll> r=find_journey(n, m, u, v);
//~ for(ll k:r) cout<<k<<" ";
//~ return 0;
//~ }
