#include <bits/stdc++.h>
using namespace std;
const int NMAX = 100004;

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

int n, m;
vector<int> adj[NMAX];
vector<int> adj_rev[NMAX];
vector<bool> used;
vector<int> order;
vector<vector<int>> components;
vector<int> component;

void dfs1(int v)
{
    used[v] = true;
    for (int u : adj[v])
    {
        if (!used[u])
        {
            dfs1(u);
        }
    }
    order.push_back(v);
}

void dfs2(int v)
{
    used[v] = true;
    component.push_back(v);
    for (int u : adj_rev[v])
    {
        if (!used[u])
        {
            dfs2(u);
        }
    }
}

int main()
{
    fin >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        int a, b;
        fin >> a >> b;
        adj[a].push_back(b);
        adj_rev[b].push_back(a);
    }
    used.assign(n + 1, false);
    for (int i = 1; i <= n; i++)
    {
        if (!used[i])
        {
            dfs1(i);
        }
    }
    reverse(order.begin(), order.end());
    used.assign(n + 1, false);
    for (int v : order)
    {
        if (!used[v])
        {
            dfs2(v);
            components.push_back(component);
            component.clear();
        }
    }
    fout << components.size() << '\n';
    for (auto comp : components)
    {
        for (auto v : comp)
        {
            fout << v << ' ';
        }
        fout << '\n';
    }
    return 0;
}