#include "islands.h"
#include<bits/stdc++.h>
using namespace std;
vector<int> p, c, t;
vector<int> U, V;
vector<vector<int>> g;
void dfs(int cur){
if (!c.empty()) return;
for (int e : g[cur]){
if (!c.empty()) return;
int next = U[e]+V[e]-cur;
if (p[next] == -1) dfs(next);
else {
c.push_back(1);
return;
}
}
}
variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V){
::U = U;
::V = V;
g.resize(N);
for (int i=0; i<M; i+=2) g[U[i]].push_back(i);
p.resize(N, -1);
dfs(0);
if (c.empty()) return false;
return true;
}
