#include <bits/stdc++.h>
using namespace std;
typedef int ll;
typedef tuple<ll, ll, ll> plll;
typedef vector<plll> vplll;
typedef pair<ll, ll> pll;
typedef vector<ll> vll;
typedef vector<pll> vpll;
typedef vector<vector<pll>> vvpll;
typedef vector<vector<ll>> vvll;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;
#define loop(i, s, e) for (ll i = (s); i < (e); ++i)
#define loopr(i, e, s) for (ll i = (e)-1; i >= (s); --i)
#define all(a) a.begin(), a.end()
const ll inf = 1e9 + 7;
ll n;
vvll g;
vb vis;
ll in = 0;
ll cnt1 = 0, cnt2 = 0;
bool is = 1;
vll del;
void dfs(ll ch, ll node, ll par) {
vis[node] = 1;
in++;
ll dar = 0;
for (auto it : g[node]) {
if (it==par && it!= ch) dar++;
if (it==ch || it == par) continue;
if (vis[it]) {
is = false;
continue;
}
dar++;
dfs(ch, it, node);
}
if (dar!= 1 && dar!= 2) is = false;
if (dar==1) cnt1++;
if (dar==2) cnt2++;
}
void Init(int N_) {
n= N_;
g.resize(n);
del.resize(n,1);
vis.resize(n, false);
}
void Link(int a, int b) {
g[a].push_back(b);
g[b].push_back(a);
}
int CountCritical() {
ll ans = 0;
loop(i,0,n) {
if (del[i]== -1) continue;
bool b = 1;
vis.assign(n,false);
loop(j,0,n) {
if (j!=i && !vis[j]) {
in = 0;
cnt1 = 0, cnt2 = 0;
is = 1;
dfs(i,j,-1);
if (in==1) continue;
if (!is || cnt1!=2 || cnt2!=(in-2)) {
b = false;
}
}
}
if (b) ans++;
else del[i] = -1;
}
return ans;
}
