#ifndef EVAL
#include"grader.cpp"
#endif
#include<bits/stdc++.h>
using namespace std;
vector<int>g[5005];
bool on[5005],vis[5005];
int n,deg[5005];
bool dfs(int v,int p){
bool flag=false;
vis[v]=true;
for(int to:g[v])if(to!=p){
if(on[to])continue;
if(flag)return false;
if(vis[to])return false;
if(!dfs(to,v))return false;
flag=true;
}
return true;
}
bool check(){
for(int i=0;i<n;i++)vis[i]=0;
for(int i=0;i<n;i++)if(!on[i]&&!vis[i]&°[i]<2)if(!dfs(i,i))return false;
for(int i=0;i<n;i++)if(!vis[i]&&!on[i])return false;
return true;
}
void Init(int N){n=N;}
void Link(int x,int y){
g[x].push_back(y);
g[y].push_back(x);
deg[x]++;
deg[y]++;
}
int CountCritical(){
int cnt=0;
for(int i=0;i<n;i++){
on[i]=true;
for(auto to:g[i])deg[to]--;
cnt+=check();
for(auto to:g[i])deg[to]++;
on[i]=false;
}
return cnt;
}
/*
7 13
-1
1 2
-1
0 5
-1
2 0
-1
3 2
-1
3 5
-1
4 3
-1
*/
