#include "islands.h"
#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define fr first
#define sc second
#define mp make_pair
const int maxn = 2e5+10;
int n, m, tin[maxn], low[maxn], mark[maxn], iscyc[maxn], can0[maxn], timer;
vector<int> g[maxn], gt[maxn];
vector<pair<int,int>> gid[maxn];
map<int,vector<int>> boats[maxn];
vector<int> cur, final;
int cycbeg = -1;
void dfs(int u, int ant) {
if(g[u].size() >= 3 || (g[u].size() == 2 && u == 0)) {
final = cur;
vector<int> i1s;
for(auto x : gid[u]) {
if(i1s.size() != 2 && x.sc/2 != ant/2) i1s.pb(x.sc);
}
final.pb(i1s[0]);
final.pb(i1s[1]);
int aux = final.size();
for(int i = aux-3; i >= 0; i++) {
final.pb(final[i]);
}
}
if(final.size()) return;
for(auto V : gid[u]) if(V.sc/2 != ant/2) {
if(final.size()) return;
cur.pb(V.sc);
dfs(V.fr,V.sc);
cur.pop_back();
}
}
void dfs0(int u) {
can0[u] = 1;
for(auto v : g[u]) {
if(can0[v] == 0) dfs0(v);
}
}
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++) {
g[U[i]].pb(V[i]);
gid[U[i]].pb(mp(V[i],i));
gt[V[i]].pb(U[i]);
boats[U[i]][V[i]].pb(i);
}
dfs(0,-10);
dfs0(0);
if(final.size()) {
return final;
}
return false;
}
