#include <bits/stdc++.h>
using namespace std;

ifstream in("ctc.in");
ofstream out("ctc.out");

const int MAXN = 1e5;

int N, M;
bool visited[MAXN + 1];
vector<int> order;
vector<int> G[MAXN + 1], T[MAXN + 1];
vector<int> compNodes[MAXN + 1];

// compNodes[i] = vector<int>
// compNodes[i] = multimea nodurilor componentei i

void dfs(int u) {
    visited[u] = true;
    for (int v : G[u]) {
        if (!visited[v]) {
            dfs(v);
        }
    }
    order.push_back(u);
}

void dfsT(int u, int compId) {
    // Nodul u face parte din comp. compId
    compNodes[compId].push_back(u);
    visited[u] = true;
    for (int v : T[u]) {
        if (!visited[v]) {
            dfsT(v, compId);
        }
    }
}

int main() {
    in >> N >> M;
    for (int i = 0; i < M; i++) {
        int u, v; in >> u >> v;
        G[u].push_back(v);
        T[v].push_back(u);
    }

    for (int i = 1; i <= N; i++) {
        if (!visited[i]) {
            dfs(i);
        }
    }
    reverse(order.begin(), order.end());
    fill(visited + 1, visited + N + 1, false);

    int compCount = 0;
    for (int i = 0; i < N; i++) {
        int u = order[i];
        if (!visited[u]) {
            dfsT(u, compCount);
            compCount++;
        }
    }

    out << compCount << "\n";
    for (int i = 0; i < compCount; i++) {
        for (int node : compNodes[i]) {
            out << node << " ";
        }
        out << "\n";
    }
    return 0;
}