/*
______ _____ _______ _ _ _______ __ _ _____ _ _ _
|_____/ | | | |____/ |______ | \ | | | | | |
| \_ |_____| |_____ | \_ ______| | \_| |_____| |__|__|
. . . . . .
_\/ \/_ _\/ \/_ _\/ \/_
_\/\/_ _\/\/_ _\/\/_
_\_\_\/\/_/_/_ _\_\_\/\/_/_/_ _\_\_\/\/_/_/_
/ /_/\/\_\ \ / /_/\/\_\ \ / /_/\/\_\ \
_/\/\_ _/\/\_ _/\/\_
/\ /\ /\ /\ /\ /\
' ' ' ' ' '
*/
#pragma GCC optimize ("O3")
#pragma GCC target ("avx2")
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <climits>
#include <cstdint>
#include <cmath>
#include <chrono>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_set>
#include <unordered_map>
#include <vector>
using namespace std;
const int MX=1e6+5;
int n;
vector<int> adj[MX];
int visitados[MX];
void Init(int N) {
n=N;
}
void Link(int A, int B) {
adj[A].push_back(B);
adj[B].push_back(A);
}
int dfs(int s, int p, int pro){
visitados[s]=1;
int ans=0;
for(auto u: adj[s]){
if(u!=p && u!=s && u!=pro){
if(visitados[u]) return 1;
else ans+=dfs(u,s,pro);
}
}
return ans>0;
}
int f(int u){
for(int i=0; i<n; i++) visitados[i]=0;
for(int i=0; i<n; i++){
if(i!=u && !visitados[i]){
if(dfs(i,-1,u)){
return 0;
}
}
}
for(int i=0; i<n; i++){
if(i==u) continue;
vector<int> v;
for(auto y: adj[i]) if(y!=u) v.push_back(y);
if(v.size()>2) return 0;
}
return 1;
}
int CountCritical() {
int ans=0;
for(int i=0; i<n; i++) if(f(i)) ans++;//, cout<<i<<" ";
return ans;
}
