#include <bits/stdc++.h>
#include <variant>
#define f first
#define s second
#define ent '\n'
using namespace std;
typedef long long ll;
const int maxn = 2e5 + 12;
const int mod = 1e9 + 2022;
map<int, int> a[maxn];
vector<int> g[maxn];
int n, m;
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++){
a[u[i]][v[i]] = i;
g[u[i]].push_back(i);
}
vector<int> ans;
if(g[0].size() >= 2){
int x = v[g[0][0]], y = v[g[0][1]];
if(x == y){
int l = -1, r = -1;
for(int i:g[x]){
if(v[i] == 0){
if(l == -1){
l = i;
}
else{
r = i;
}
}
}
ans = {g[0][0], l, g[0][1], r, l, g[0][0], r, g[0][1]};
return ans;
}
ans = {g[0][0], a[x][0], g[0][1], a[y][0], a[x][0], g[0][0], a[y][0], g[0][1]};
return ans;
}
if(g[0].size() == 0) return false;
int x = v[g[0][0]], sz = 1, y = 0;
ans = {g[0][0]};
while(g[x].size() == 2){
int t = 0;
if(v[g[x][t]] == y){
t++;
}
ans.push_back(g[x][t]);
y = x;
x = v[g[x][t]];
sz++;
}
if(g[x].size() <= 1) return false;
int l = -1, r = -1;
for(int i:g[x]){
if(v[i] == y){
y = -1;
continue;
}
if(l == -1){
l = v[i];
}
else if(r == -1){
r = v[i];
}
}
vector<int> t = {a[x][l], a[l][x], a[x][r], a[r][x], a[l][x], a[x][l], a[r][x], a[x][r]};
for(int x:t){
ans.push_back(x);
}
for(int i=sz-1;i>=0;i--){
ans.push_back(ans[i]);
}
return ans;
}
