#include <bits/stdc++.h>
#define mp(x...) array<int, 2>({x})
#define pb push_back
#include "islands.h"
using namespace std;
#ifdef DEBUGGING
#include "../debug.h"
#else
#define debug(x...) void(42)
#endif
int n, m;
vector<int> u, v;
variant<bool, vector<int>> subtask1()
{
if (n <= 2)
return false;
array<array<int, 3>, 3> a;
for (int i = 0; i < m; i++)
if (u[i] <= 2 && v[i] <= 2)
a[u[i]][v[i]] = i;
debug(a);
return vector<int>({a[0][1], a[1][2], a[2][0], a[0][2], a[2][1], a[1][0], a[2][0], a[1][2], a[0][1], a[1][0], a[2][1], a[0][2]});
}
constexpr static int MXN = 1e5;
bitset<MXN> visited;
vector<array<int, 2>> res;
vector<array<int, 2>> g[MXN];
bool dfs(int node, int le)
{
res.pb(mp(node, le));
visited[node] = true;
for (auto [c, e] : g[node])
{
if ((e/2) == (le/2))
continue;
if (visited[c])
{
res.pb({c, e});
return true;
}
else if (dfs(c, e))
{
return true;
}
}
res.pop_back();
return false;
}
static inline int get_reverse(int i)
{
return (i / 2) * 2 + 1 - (i&1);
}
variant<bool, vector<int>> subtask2()
{
for (int i = 0; i < m; i++)
{
debug(i, u[i], v[i]);
g[u[i]].pb(mp(v[i], i));
}
if(dfs(0, -1))
{
vector<int> out;
debug(res);
int lsn = res.back()[0];
// Go to the loop
int i;
for (i = 0; res[i][0] != lsn; i++)
if (i != 0)
out.pb(res[i][1]);
debug(out);
// Cycle in loop
for (int j = i+1; j < res.size(); j++)
out.pb(res[j][1]);
debug(out);
// Cycle back in loop
for (int j = res.size()-1; j > i; j--)
out.pb(get_reverse(res[j][1]));
debug(out);
// Cycle in loop again
for (int j = i+1; j < res.size(); j++)
out.pb(res[j][1]);
debug(out);
// Cycle back again
for (int j = res.size()-1; j > i; j--)
out.pb(get_reverse(res[j][1]));
debug(out);
// Come back
for (int j = i; j >= 1; j--)
out.pb(res[j][1]);
debug(out);
return out;
}
return false;
}
variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V)
{
n = N;
m = M;
u = U;
v = V;
return subtask2();
assert(false);
}
