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

using namespace std;

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

const int SIZE = 100005;

int n, m, cnt;
bool visited[SIZE];

vector <int> adj[SIZE], adj_t[SIZE];
vector <int> ssc[SIZE];

stack <int> s;

void Read()
{
    f >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        int x, y;
        f >> x >> y;
        adj[x].push_back(y);
        adj_t[y].push_back(x);
    }
}

void DFS1(int node)
{
    visited[node] = true;
    for (unsigned int i = 0; i < adj[node].size(); i++)
    {
        int neighbour = adj[node][i];
        if (visited[neighbour] == false)
        {
            DFS1(neighbour);
        }
    }
    s.push(node);
}

void DFS2(int node)
{
    ssc[cnt].push_back(node);
    visited[node] = false;
    for (unsigned int i = 0; i < adj_t[node].size(); i++)
    {
        int neighbour = adj_t[node][i];
        if (visited[neighbour] == true)
        {
            DFS2(neighbour);
        }
    }
}

void Solve()
{
    for (int i = 1; i <= n; i++)
    {
        if (visited[i] == false)
        {
            DFS1(i);
        }
    }

    while (s.empty() == false)
    {
        int node = s.top();
        s.pop();

        if (visited[node] == true)
        {
            cnt++;
            DFS2(node);
        }
    }
}

void Print()
{
    g << cnt << "\n";
    for (int i = 1; i <= cnt; i++)
    {
        for (unsigned int j = 0; j < ssc[i].size(); j++)
        {
            g << ssc[i][j] << " ";
        }
        g << "\n";
    }
}

int main()
{
    Read();
    Solve();
    Print();

    return 0;
}