#include <fstream>
#include <vector>

using namespace std;

vector<vector<int>> graph;
vector<vector<int>> transposed_graph;
vector<bool> visited;
vector<int> node_order;
vector<vector<int>> components;
int componentCount = 0;

void dfs1(const int node)
{
    if (visited[node])
        return;

    visited[node] = true;
    for (auto neighbor : graph[node])
        dfs1(neighbor);

    node_order.push_back(node);
}

void dfs2(const int node)
{
    if (visited[node])
        return;

    visited[node] = true;

    components[componentCount].push_back(node);
    
    for (auto neighbor : transposed_graph[node])
        dfs2(neighbor);
}

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

    int n, m;
    fin >> n >> m;

    graph = vector<vector<int>>(n, vector<int>());
    transposed_graph = vector<vector<int>>(n, vector<int>());
    visited = vector<bool>(n, false);
    node_order = vector<int>();
    node_order.reserve(n);

    for (auto i = 0; i < m; i++)
    {
        int x, y;
        fin >> x >> y;
        x--;
        y--;

        graph[x].push_back(y);
        transposed_graph[y].push_back(x);
    }

    fin.close();

    for (auto i = 0; i < n; i++)
        if (!visited[i])
            dfs1(i);

    for (auto&& i : visited)
        i = false;

    auto num_components = 0;
    
    for (auto i = static_cast<int>(node_order.size()) - 1; i >= 0; i--)
    {
        const auto node = node_order[i];

        components.emplace_back();

        if (!visited[node])
            dfs2(node);

        componentCount++;

        if (!components[componentCount - 1].empty())
            num_components++;
    }

    fout << num_components << endl;
    for (auto& component : components)
    {
        if (!component.empty())
        {
            for (auto node : component)
                fout << node + 1 << " ";
            fout << endl;
        }
    }

    fout.close();
    return 0;
}