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

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

const int NMAX=1e5;
int n,m,i,node1,node2,sol;
bool viz[NMAX+5];
vector <int> edge[NMAX+5],t_edge[NMAX+5],comp_conex[NMAX+5];
stack <int> s;

void dfs(int node)
{
    viz[node]=1;

    for (auto x: edge[node])
        if (!viz[x])
            dfs(x);

    s.push(node);
}

void t_dfs(int node)
{
    viz[node]=1;
    comp_conex[sol].push_back(node);

    for (auto x: t_edge[node])
        if (!viz[x])
            t_dfs(x);
}

int main()
{
    ios_base::sync_with_stdio(false);
    fin.tie(0); fout.tie(0);

    fin>>n>>m;
    while (m--)
    {
        fin>>node1>>node2;
        edge[node1].push_back(node2);
        t_edge[node2].push_back(node1);
    }

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

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

    while (!s.empty())
    {
        node1=s.top();
        s.pop();

        if (viz[node1])
            continue;

        sol++;
        t_dfs(node1);
    }

    fout<<sol<<'\n';

    for (i=1; i<=sol; i++)
    {
        for (auto x: comp_conex[i])
            fout<<x<<" ";
        fout<<'\n';
    }


    return 0;
}