This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include "islands.h"
#include <bits/stdc++.h>
using namespace std;
#define sp " "
#define endl "\n"
#define pii pair<int, int>
#define st first
#define nd second
#define fileio() freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout)
#define fastio() cin.tie(0), ios_base::sync_with_stdio(0)
#define pb push_back
#define LL node * 2
#define RR node * 2 + 1
#define ll long long
#define MAXN 300005
const int modulo = 1e9 + 7;
const ll INF = 2e18 + 7;
vector<pii> in[MAXN], out[MAXN];
variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V) {
    for (int i = 0; i < M; i++){
        in[V[i]].pb({U[i], i});
        out[U[i]].pb({V[i], i});
    }
    if (N == 2){
        if (out[0].size() >= 2 && in[0].size() >= 1){
            int a = out[0][0].nd, b = out[0][1].nd, c = in[0][0].nd;
            vector<int> v = {a, c, b, a, c, b};
            return v;
        }
        return false;
    }
    int a = -1, b = -1, c = -1, d = -1;
    for (auto i : out[0]) {
        if (i.st == 1) a = i.nd;
        if (i.st == 2) c = i.nd;
    }
    for (auto i : in[0]) {
        if (i.st == 1) b = i.nd;
        if (i.st == 2) d = i.nd;
    }
    if (a != -1 && b != -1 && c != -1 && d != -1){
        vector<int> v = {a, b, c, d, b, a, d, c};
        return v;
    }
    
    return false;
}
/*
int main() {
    fileio();
    int N, M;
    assert(2 == scanf("%d %d", &N, &M));
    std::vector<int> U(M), V(M);
    for (int i = 0; i < M; ++i) {
    assert(2 == scanf("%d %d", &U[i], &V[i]));
    }
    std::variant<bool, std::vector<int>> result = find_journey(N, M, U, V);
    if (result.index() == 0) {
    printf("0\n");
    if (std::get<bool>(result)) {
      printf("1\n");
    } else {
      printf("0\n");
    }
    } else {
    printf("1\n");
    std::vector<int> &canoes = std::get<std::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;
}
*/
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