#include "islands.h"
#include <bits/stdc++.h>
using namespace std;
vector<vector<array<int, 2>>> g;
vector<map<int, int>> connected;
vector<int> color, par, nett;
int x, y;
bool dfs(int u, int p){
par[u] = p;
if(color[u]==2) return false;
color[u] = 1;
if(nett[u]){
return true;
}
for(auto [v, e]:g[u]){
if(v==p)
continue;
if(color[v]==1){
x = v;
y = u;
return true;
}
if(dfs(v, u)){
return true;
}
}
color[u] = 2;
return false;
}
std::variant<bool, std::vector<int>> find_journey(int N, int M, std::vector<int> U, std::vector<int> V) {
g.assign(N, {});
connected.assign(N, {});
color.assign(N, {});
par.assign(N, {});
nett.assign(N, {});
for(int i=0; i<M; i++){
if(not connected[U[i]][V[i]]){
g[U[i]].push_back({V[i], i});
}
connected[U[i]][V[i]]++;
if(connected[U[i]][V[i]]>=2 and connected[V[i]][U[i]]>=1){
nett[U[i]]=1;
}
if(connected[U[i]][V[i]]>=1 and connected[V[i]][U[i]]>=2){
nett[V[i]]=1;
}
}
return dfs(0, -1);
}
