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

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

vector<vector<int>> g, gt;
vector<int> order, comp;
vector<int> visited;

void dfs1(int v) {
    visited[v] = 1;
    for (int u : g[v])
        if (!visited[u])
            dfs1(u);
    order.push_back(v);
}

void dfs2(int v) {
    visited[v] = 1;
    comp.push_back(v);
    for (int u : gt[v])
        if (!visited[u])
            dfs2(u);
}

int main() {
    int n, m;
    fin >> n >> m;
    g.assign(n + 1, {});
    gt.assign(n + 1, {});
    for (int i = 0; i < m; i++) {
        int x, y;
        fin >> x >> y;
        g[x].push_back(y);
        gt[y].push_back(x);
    }

    visited.assign(n + 1, 0);
    for (int i = 1; i <= n; i++)
        if (!visited[i])
            dfs1(i);

    visited.assign(n + 1, 0);
    vector<vector<int>> comps;
    for (int i = n - 1; i >= 0; i--) {
        int v = order[i];
        if (!visited[v]) {
            comp.clear();
            dfs2(v);
            comps.push_back(comp);
        }
    }

    fout << comps.size() << "\n";
    for (auto &c : comps) {
        for (int v : c) fout << v << " ";
        fout << "\n";
    }
    return 0;
}