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

using namespace std;

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

vector<vector<int>> adj, revAdj, components;
vector<int> visited;
stack<int> stiva;

void DFS1(int nod)
{
    visited[nod] = 1;
    for(int i = 0; i < adj[nod].size(); i++)
        if(visited[adj[nod][i]] == 0)
            DFS1(adj[nod][i]);

    stiva.push(nod);
}

void DFS2(int nod, int nrComp)
{
    components[nrComp].push_back(nod);
    visited[nod] = 1;

    for(int i = 0; i < revAdj[nod].size(); i++)
        if(visited[revAdj[nod][i]] == 0)
            DFS2(revAdj[nod][i], nrComp);
}

int main()
{
    int n, m, nod1, nod2, i, j, nrComp = 0, nod;
    in >> n >> m;

    adj.resize(n + 1);
    revAdj.resize(n + 1);
    visited.resize(n + 1);

    for(i = 1; i <= m; i++)
    {
        in >> nod1 >> nod2;
        adj[nod1].push_back(nod2);
        revAdj[nod2].push_back(nod1);
    }

    for(i = 1; i <= n; i++)
        if(visited[i] == 0)
            DFS1(i);

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

    while(!stiva.empty())
    {
        nod = stiva.top();
        stiva.pop();

        if(visited[nod] == 0)
        {
            components.push_back({});
            DFS2(nod, nrComp);
            nrComp++;
        }
    }

    out << nrComp << '\n';

    for(i = 0; i < components.size(); i++)
    {
        for(j = 0; j < components[i].size(); j++)
            out << components[i][j] << " ";
        out << '\n';
    }

    return 0;
}