Lesson12

#include <algorithm>
#include <array>
#include <cassert>
#include <climits>
#include <cmath>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#define all(x) x.begin(), x.end()
using namespace std;
using ll=long long;
const double eps = 1e-10;
const int mod = 1000000007;

void DFS(const vector<vector<int>>& g, int u, vector<bool>& used, vector<int>& to_go) {
  used[u] = true;
  for (int v : g[u]) {
    if (!used[v]) {
      DFS(g, v, used, to_go);
    }
  }
  to_go.push_back(u);
}
vector<int> DFSGo(const vector<vector<int>>& h) {
  int n = h.size();
  vector<bool> used(n);
  vector<int> to_go(n);
  for (int u = 0; u < n; ++u) {
    if (!used[u]) {
      DFS(h, u, used, to_go);
    }
  }
  return to_go;
}

void DFSKss(const vector<vector<int>>& g, int u, vector<int>& kss, int comp) {
  kss[u] = comp;
  for (int v : g[u]) {
    if (kss[v] == -1) {
      DFSKss(g, v, kss, comp);
    }
  }
}
vector<set<int>> Condense(const vector<vector<int>>& g) {
  int n = g.size();
  vector<vector<int>> h(n);
  for (int u = 0; u < n; ++u) {
    for (int v : g[u]) h[v].push_back(u);
  }

  vector<int> to_go = DFSGo(h);
  reverse(all(to_go));
  vector<int> kss(n, -1);
  int comp = 0;
  for (int u : to_go) {
    if (kss[u] == -1) {
      DFSKss(g, u, kss, comp++);
    }
  }
  vector<set<int>> condensed(comp);
  for (int u = 0; u < n; ++u) {
    for (int v : g[u]) {
      if (kss[u] == kss[v]) continue;
      condensed[kss[u]].insert(kss[v]);
    }
  }
  return condensed;
}

void Solve() {
  int n, e; cin >> n >> e;
  vector<vector<int>> g(n);
  for (int i = 0; i < e; ++i) {
    int u, v; cin >> u >> v;
    g[u].push_back(v);
  }
  auto condense = Condense(g);
  for (int u = 0; u < condense.size(); ++u) {
    cout << u << ": ";
    for (int v : condense[u]) cout << v << " ";
    cout << "\n";
  }
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);

  Solve();
  return 0;
}