#include <bits/stdc++.h>


using namespace std;

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

const int Nmax = 100005;

vector < int > L[Nmax];

vector < int > H[Nmax];

vector < int > Sol[Nmax];

int a[Nmax] , n , m , k , ans;

bool viz[Nmax];

void DFS(int nod)
{
    viz[nod] = true;
    for(auto it : L[nod])
        if(!viz[it])
            DFS(it);
    a[++k] = nod;
}

void DFS1(int nod)
{
    viz[nod] = 1;
    Sol[ans].push_back(nod);
    for(auto it : H[nod])
        if(!viz[it])
            DFS1(it);
}

int main()
{
    int x , y;
    fin >> n >> m;
    for(int i = 1 ; i <= m ; i++)
    {
        fin >> x >> y;
        L[x].push_back(y);
        H[y].push_back(x);
    }
    for(int i = 1 ; i <= n ; i++)
        if(!viz[i])
            DFS(i);
    for(int i = 1 ; i <= n ; i++)
        viz[i] = false;
    for(int i = k ; i >= 1 ; i--)
        if(!viz[a[i]])
    {
        ans++;
        DFS1(a[i]);
    }
    fout << ans << '\n';
    for(int i = 1 ; i <= ans ; i++)
    {
        for(auto it : Sol[i])
            fout << it << " ";
        fout << "\n";
    }
    fin.close();
    fout.close();
}