#include <bits/stdc++.h>
using namespace std;
variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V) {
if (N == 2) {
vector<int> rig, lef;
for (int i = 0; i < M; ++i) {
if (U[i] == 0) {
lef.push_back(i);
} else {
rig.push_back(i);
}
}
if (lef.size() < 2 || rig.empty()) {
return false;
}
return vector<int>({lef[0], rig[0], lef[1], lef[0], rig[0], lef[1]});
}
vector<vector<pair<int, int>>> adj(N);
for (int i = 0; i < M; ++i) {
if (i % 2 == 0) {
adj[U[i]].push_back({V[i], i});
adj[V[i]].push_back({U[i], i});
}
}
vector<bool> vis(M), vis_node(N);
int cycle = 0;
auto dfs = [&](auto &&self, int u, int edn) {
if (edn != -1) {
if (vis[edn]) {
return;
}
vis[edn] = true;
}
if (vis_node[u]) {
cycle = 1;
return;
}
vis_node[u] = true;
for (auto &[i, edc] : adj[u]) {
if (edc == edn) { continue; }
self(self, i, edc);
if (cycle) {
return;
}
}
};
dfs(dfs, 0, -1);
if (!cycle) {
return false;
}
return true;
}
#ifdef MACOS_LOCAL
#include "grader.cpp"
#endif
