#include <fstream>
#include <vector>
#include <stack>
#include <cstring>
#include <bitset>

using namespace std;

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

#define MAX_N 100000

int n, m, strongConnectedComponentsNumber;
vector < vector <int> > graph, transposedGraph, components;
bitset <MAX_N + 1> visited;
stack <int> order;

void readGraph()
{
    in >> n >> m;
    graph.resize(n + 1);
    transposedGraph.resize(n + 1);
    for(int i = 1; i <= m; i++)
    {
        int a, b;
        in >> a >> b;
        graph[a].push_back(b);
        transposedGraph[b].push_back(a);
    }
}

void dfs1(int node)
{
    visited[node] = 1;
    for(int x : graph[node])
        if(!visited[x])
            dfs1(x);
    order.push(node);
}

void dfs2(int node)
{
    visited[node] = 1;
    components[strongConnectedComponentsNumber].push_back(node);
    for(int x : transposedGraph[node])
        if(!visited[x])
            dfs2(x);
}

void printComponents()
{
    out << strongConnectedComponentsNumber << "\n";
    for(int i = 0; i < strongConnectedComponentsNumber; i++)
    {
        for(int node : components[i])
            out << node << " ";
        out << "\n";
    }
}

int main()
{
    readGraph();

    for(int i = 1; i <= n; i++)
    {
        if(!visited[i])
            dfs1(i);
    }

    for(int i = 1; i <= n; i++)
        visited[i] = 0;

    components.resize(n);

    while(!order.empty())
    {
        int node = order.top();
        if(!visited[node])
        {
            dfs2(node);
            ++ strongConnectedComponentsNumber;
        }
        order.pop();
    }

    printComponents();
    return 0;
}