#include <vector>
using namespace std;
#define MAXN 1000006
#define mp make_pair
#define pb push_back
#define sz(v) ((int)(v).size())
typedef pair<int,int> pii;
static int N,deg[MAXN],par[MAXN],size[MAXN];
static int _par[4][MAXN],_deg[4][MAXN],_target[4];
static int cycle_cnt,cycle_size;
static bool sw,_valid[4];
static vector<pii> edges;
int find(int n,int p[MAXN]=par){ return p[n]==n?n:(p[n]=find(p[n],p)); }
void Init(int n)
{
int i;
N = n;
for (i=1;i<=N;i++) par[i] = i, size[i] = 1;
}
void addEdge(int a,int b)
{
int i;
for (i=0;i<4;i++){
if (_target[i] == a || _target[i] == b) continue;
if (++_deg[i][a] == 3) _valid[i] = 0;
if (++_deg[i][b] == 3) _valid[i] = 0;
int p = find(a,_par[i]), q = find(b,_par[i]);
if (p == q) _valid[i] = 0;
_par[i][q] = p;
}
}
void reg(int n)
{
int i,j,k=0;
_target[k++] = n;
for (i=0;i<sz(edges);i++){
if (edges[i].first == n) _target[k++] = edges[i].second;
if (edges[i].second == n) _target[k++] = edges[i].first;
}
for (i=0;i<4;i++){
_valid[i] = 1;
for (j=1;j<=N;j++) _par[i][j] = j;
}
for (i=0;i<sz(edges);i++) addEdge(edges[i].first,edges[i].second);
}
void Link(int a,int b)
{
a++; b++;
deg[a]++; deg[b]++;
edges.pb(mp(a,b));
if (!sw && deg[a] == 3) sw = 1, reg(a);
else if (!sw && deg[b] == 3) sw = 1, reg(b);
else if (!sw){
a = find(a); b = find(b);
if (a == b){
cycle_cnt++;
cycle_size = size[a];
}else{
par[b] = a;
size[a] += size[b];
}
}else{
addEdge(a,b);
}
}
int CountCritical()
{
if (cycle_cnt > 1) return 0;
if (!sw){
if (cycle_cnt) return cycle_size;
return N;
}
int ret = 0,i;
for (i=0;i<4;i++) ret += _valid[i];
return ret;
}
