#include "islands.h"
#include <bits/stdc++.h>
//#include "grader.cpp"
using namespace std;
int const mxN = 1e3+5;
vector<pair<int,int>> adj[mxN], adj2[mxN];
int n,m, cnt[mxN][mxN];
bool vis[mxN], poss[mxN];
vector<int> from[mxN];
bool flag = 0;
vector<int> st, fin;
void solve( int i , int p) {
int fi=-1,se=-1,th=-1,fo=-1, n1 = 0,n2 = 0;
for(auto it:adj[i]) {
if(it.first==p) continue;
if(fi==-1) { fi = it.second; n1 = it.first; }
else if(se==-1) { se = it.second; n2 = it.first; }
}
for(auto it:adj[n1]) {
if(it.first==i) {
if(th==-1) th = it.second;
else fo = it.second;
}
}
for(auto it:adj[n2]) {
if(it.first==i) {
if(fo==-1) fo = it.second;
}
}
fin = {fi,th,se,fo,th,fi,fo,se};
}
void dfs ( int i ) {
for(auto it:adj[i]) {
if(vis[it.first]) continue;
vis[it.first] = 1;
st.push_back(it.second);
if(adj[it.first].size()>2) { flag = 1; solve(it.first,i); return; }
dfs(it.first);
}
}
variant<bool,vector<int>> find_journey( int N, int M,vector<int> U, vector<int> V) {
n = N, m = M;
for(int i=0; i<m; i++) { adj[U[i]].push_back({V[i],i}), adj2[V[i]].push_back({U[i],i}); cnt[U[i]][V[i]]++; }
vector<int> v;
if(adj[0].size()>1) { solve(0,-1); return fin; }
else {
vis[0] = 1; dfs(0);
}
if(flag) {
vector<int> tot = st;
for(auto it:fin) tot.push_back(it);
reverse(st.begin(),st.end());
for(auto it:st) tot.push_back(it);
return tot;
}
return false;
}
