#include "islands.h"
#include <bits/stdc++.h>
#include <variant>
using namespace std;
const int MAX = 1e5 + 5;
int N;
bool mark[MAX];
vector<vector<vector<int>>> g;
vector<int> path, special;
bool dfs(int u, int p) {
if (mark[u])
return false;
mark[u] = true;
for (int v = 0; v < N; v++) {
if (v != p && !g[u][v].empty()) {
if (!v) {
path.push_back(0);
return true;
}
if (dfs(v, u)) {
path.push_back(v);
return true;
}
}
}
return false;
}
bool dfsSpecial(int u, int p) {
if (mark[u])
return false;
mark[u] = true;
if (special[u] != -1) {
path.push_back(special[u]);
path.push_back(u);
return true;
}
for (int v = 0; v < N; v++)
if (v != p && !g[u][v].empty())
if (dfsSpecial(v, u)) {
path.push_back(u);
return true;
}
return false;
}
variant<bool, vector<int>> find_journey(int _N, int M, vector<int> U, vector<int> V) {
N = _N;
if (N == 2) {
vector<int> g[2];
for (int i = 0; i < M; i++)
g[U[i]].push_back(i);
if (g[0].size() < 2 || g[1].empty())
return false;
return vector<int>({g[0][0], g[1][0], g[0][1], g[0][0], g[1][0], g[0][1]});
}
g.resize(N, vector<vector<int>>(N));
for (int i = 0; i < M; i++)
g[U[i]][V[i]].push_back(i);
bool isClique = true;
for (int i = 0; i < N && isClique; i++)
for (int j = 0; j < N && isClique; j++)
if (i != j && g[i][j].empty())
isClique = false;
if (isClique)
return vector<int>({g[0][1][0], g[1][2][0], g[2][0][0], g[0][2][0], g[2][1][0], g[1][0][0],
g[2][0][0], g[1][2][0], g[0][1][0], g[1][0][0], g[2][1][0], g[0][2][0]});
special.resize(N, -1);
for (int i = 0; i < N; i++)
for (int j = 0; j < N; j++)
if (i != j && g[i][j].size() >= 2 && g[j][i].size() >= 1)
special[i] = j;
if (dfsSpecial(0, 0)) {
reverse(path.begin(), path.end());
vector<int> rs;
for (int i = 0; i < path.size() - 2; i++)
rs.push_back(g[path[i]][path[i + 1]][0]);
int u = path[path.size() - 2], v = path.back();
rs.push_back(g[u][v][0]);
rs.push_back(g[v][u][0]);
rs.push_back(g[u][v][1]);
rs.push_back(g[u][v][0]);
rs.push_back(g[v][u][0]);
rs.push_back(g[u][v][1]);
for (int i = (int) path.size() - 3; i >= 0; i--)
rs.push_back(g[path[i]][path[i + 1]][0]);
return rs;
}
path.clear();
for (int i = 0; i < N; i++)
mark[i] = false;
bool isDoubled = M % 2 == 0;
for (int i = 1; i < M && isDoubled; i += 2)
if (U[i - 1] != U[i] || V[i - 1] != V[i])
isDoubled = false;
if (isDoubled) {
if (dfs(0, 0)) {
path.push_back(0);
reverse(path.begin(), path.end());
vector<int> rs;
for (int t = 1; t < path.size(); t++) {
for (int i = 0; i < path.size() - 1; i++)
rs.push_back(g[path[i]][path[i + 1]][0]);
for (int i = 0; i < path.size() - 1; i++)
rs.push_back(g[path[i]][path[i + 1]][1]);
}
return rs;
}
return false;
}
return false;
}
//int main() {
// freopen("../_input", "r", stdin);
// int N, M;
// assert(2 == scanf("%d %d", &N, &M));
//
// vector<int> U(M), V(M);
// for (int i = 0; i < M; ++i) {
// assert(2 == scanf("%d %d", &U[i], &V[i]));
// }
//
// variant<bool, vector<int>> result = find_journey(N, M, U, V);
// if (result.index() == 0) {
// printf("0\n");
// if (get<bool>(result)) {
// printf("1\n");
// } else {
// printf("0\n");
// }
// } else {
// printf("1\n");
// vector<int> &canoes = get<vector<int>>(result);
// printf("%d\n", static_cast<int>(canoes.size()));
// for (int i = 0; i < static_cast<int>(canoes.size()); ++i) {
// if (i > 0) {
// printf(" ");
// }
// printf("%d", canoes[i]);
// }
// printf("\n");
// }
// return 0;
//}
