#include <bits/stdc++.h>
#define eb emplace_back
#define printv(a, b) {\
for(auto pv : a) b << pv << " ";\
b << "\n";\
}
using namespace std;
int n;
vector<vector<int>> g;
vector<int> in, low;
vector<int> pr;
void Init(int N){
n = N;
g.resize(n);
}
void Link(int u, int v){
g[u].eb(v);
g[v].eb(u);
}
int ts = 0;
void dfs(int now, int p){
in[now] = ts++;
low[now] = in[now];
pr[now] = p;
for(int i : g[now]){
if(in[i] != -1){
low[now] = min(low[now], in[i]);
continue;
}
dfs(i, now);
low[now] = min(low[now], low[i]);
}
}
int CountCritical(){
ts = 0;
in.clear();
low.clear();
pr.clear();
in.resize(n, -1);
low.resize(n);
pr.resize(n);
int con = 0;
for(int i = 0; i < n; i++){
if(in[i] != -1) continue;
con++;
dfs(i, i);
}
int zero = 0, one = 0, two = 0, more = 0;
for(int i = 0; i < n; i++){
int deg = g[i].size();
if(deg == 0) zero++;
else if(deg == 1) one++;
else if(deg == 2) two++;
else more++;
}
int ans = 0;
/*cerr << "query " << one << " " << two << " " << more << " " << con << "\n";
printv(in, cerr);
printv(low, cerr);
printv(pr, cerr);*/
for(int i = 0; i < n; i++){
int deg = g[i].size();
if(deg == 0) zero--;
else if(deg == 1) one--;
else if(deg == 2) two--;
else more--;
for(int j : g[i]){
int d = g[j].size();
if(d == 0) zero--;
else if(d == 1) one--;
else if(d == 2) two--;
else more--;
if(d - 1 == 0) zero++;
else if(d - 1 == 1) one++;
else if(d - 1 == 2) two++;
else more++;
if(pr[j] == i && low[j] >= in[i]) con++;
}
if(pr[i] == i) con--;
//cerr << "test " << i << "\n";
//cerr << one << " " << two << " " << more << " " << con << "\n";
if(more == 0 && one == (con - zero) * 2) ans++;
if(deg == 0) zero++;
else if(deg == 1) one++;
else if(deg == 2) two++;
else more++;
for(int j : g[i]){
int d = g[j].size();
if(d == 0) zero++;
else if(d == 1) one++;
else if(d == 2) two++;
else more++;
if(d - 1 == 0) zero--;
else if(d - 1 == 1) one--;
else if(d - 1 == 2) two--;
else more--;
if(pr[j] == i && low[j] >= in[i]) con--;
}
if(pr[i] == i) con++;
}
return ans;
}
