#include <iostream>
#include <fstream>
#include <vector>
#include <stack>

using namespace std;

vector<vector<int>> L;
vector<vector<int>> LT;
int n, m;

vector<bool> viz;
stack<int> st;

vector<vector<int>> sol;

int nr_componente_tare_conexe = 0;

void dfs(int node)
{
    viz[node] = true;
    for (auto v : L[node])
        if (!viz[v])
            dfs(v);
    st.push(node);
}

void dfs_T(int node)
{
    viz[node] = true;
    for (auto v : LT[node])
        if (!viz[v])
            dfs_T(v);
    sol.back().push_back(node);
}

int main()
{
    ifstream f("ctc.in");
    f >> n >> m;
    viz.resize(n + 1, false);
    L.resize(n + 1);
    LT.resize(n + 1);
    for (int i = 1; i <= m; ++i)
    {
        int a, b;
        f >> a >> b;
        L[a].push_back(b);
        LT[b].push_back(a);
    }
    f.close();

    for (int i = 1; i <= n; ++i)
        if (!viz[i])
            dfs(i);

    for (int i = 1; i <= n; ++i)
        viz[i] = false;

    while (!st.empty())
    {
        int node = st.top();
        st.pop();
        if (!viz[node])
        {
            sol.emplace_back();
            dfs_T(node);
        }
    }

    std::ofstream g("ctc.out");
    g << sol.size() << '\n';
    for (auto& comp : sol)
    {
        for (auto v : comp)
            g << v << ' ';
        g << '\n';
    }
    g.close();

    return 0;
}