#include <bits/stdc++.h>
#include <variant>
#include <vector>
#define mp make_pair
#define pb push_back
#define pll pair<long long, long long>
#define MOD 1000002022ll
#define xx first
#define yy second
using namespace std;
typedef long long ll;
multiset<ll> to[100100], from[100100];
vector<ll> braket;
ll root;
bool dead[100100];
void erase(ll cur) {
if(dead[cur]) return;
vector<ll> kill;
for(auto i:to[cur]) {
from[i].erase(from[i].find(cur));
if(i!=root&&from[i].empty()) kill.pb(i);
}
for(auto i:from[cur]) {
to[i].erase(to[i].find(cur));
if(to[i].empty()) kill.pb(i);
}
dead[cur]=true;
for(auto i:kill) erase(i);
}
variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V) {
variant<bool, vector<int>> v;
for(int i=0; i<M; i++) {
to[U[i]].insert(V[i]);
from[V[i]].insert(U[i]);
}
for(int i=0; i<N; i++) {
if(to[i].empty()||(i!=root&&from[i].empty())) erase(i);
}
if(dead[root]) {
v=false;
return v;
}
while(to[root].size()==1) {
ll t=root;
braket.pb(t);
root=*to[root].begin();
erase(t);
if(dead[root]) {
v=false;
return v;
}
}
v=true;
return v;
}
