#include <iostream>
#include<vector>
using namespace std;
#define MAXL 10000
int parent[MAXL];
int getroot(int a) {
 if (parent[a] == a) {
  return a;
 }
 else {
  parent[a] = getroot(parent[a]);//路径压缩
 }
 return parent[a];
}
bool query(int a, int b) {
 int roota = getroot(a);
 int rootb = getroot(b);
 return roota == rootb;
}
void merge(int a,int b){
 if (query(a, b)) {
  return;
 }
 int roota = getroot(a);
 int rootb = getroot(b);
 parent[b] = a;
 return;
}
int main()
{
 int n; cin >> n;//元素数目
 for (int i = 0; i < n; i++) {
  parent[i] = i;//初始父节点为自己
 }
 int m; cin >> m;//合并次数
 int a, b;
 for (int i = 0; i < m; i++) {
  cin >> a >> b;
  merge(a, b);
 }
 vector<int> result;
 int c=0;
 for (int i = 0; i < n; i++) {
  if (parent[i] == i) {
   result.push_back(i);
   c++;
  }
 }
 cout << "等价类数目: " << c << endl;
 cout << "根节点:  " << endl;
 for (int i = 0; i < result.size(); i++) {
  cout << result[i] << endl;
 }
}
/*
25
8
1 2
2 5
2 3
7 9
5 0
11 12
22 23
14 12
*/