/*
SUBTASK 1 JUST TO TEST HIPHOTESES
*/
#include <bits/stdc++.h>
#define all(x) x.begin(),x.end()
#define sz(x) (int)(x.size())
const int MAXN = 1e6+10 ;
using namespace std ;
int N ;
vector<int> adj[MAXN] ;
int disappear(int x){
//if x != -1, then I already removed someone and I can not have cycles/degree 3
//if x == -1, I can have a SINGLE cycle and the answer will be the size of cycle
//in every case, nobody can have degree three
vector<int> dsu(N) ; iota(all(dsu) , 0 ) ;
vector<int> qtd(N,1) ;
vector<int> deg(N,0) ;
int qtdCycle = 0 , sz_cycle = N ;
function<int(int)> find = [&](int a){
return dsu[a] = (a == dsu[a]) ? a : find(dsu[a]) ;
} ;
auto isCycle = [&](int a, int b){
a = find(a) ;
b = find(b) ;
if(a == b ) return true ;
if(rand() % 2 ) swap(a,b) ;
dsu[a] = b ;
qtd[b] += qtd[a] ;
return false ;
} ;
for(int i = 0 ; i < N; i++ ){
if(i == x ) continue ;
for(auto neigh : adj[i]){
if(neigh == x ) continue ;
if((++deg[i]) > 2 ) return 0 ;
if(i < neigh){
if(isCycle(i,neigh)){
qtdCycle++ ;
sz_cycle = qtd[find(i)] ;
}
}
}
}
if(x != -1 ) return qtdCycle == 0 ;
return qtdCycle <= 1 ? sz_cycle : 0 ;
}
void Init(int N_) {
N = N_;
}
void Link(int A, int B) {
adj[A].push_back(B) ;
adj[B].push_back(A) ;
}
int CountCritical() {
int ans = disappear(-1) ;
for(int i = 0 ; i < N ; i++ ){
if( sz(adj[i]) >= 3 ){
ans += disappear(i) ;
for(int j = 0 ; j < 3 ; j++ )
ans += disappear(adj[i][j]) ;
return ans ;
}
}
return ans ;
}
