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

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

const int Nmax = 100005;
int n, m, Use[Nmax], nrctc, nr, x[Nmax];
vector <int> G[Nmax], sol[Nmax], GT[Nmax];

void Read()
{
    f>>n>>m;
    while(m--)
    {
        int x, y;
        f>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

void DFS2(int nod)
{
    sol[nrctc].push_back(nod);
    Use[nod] = 0;
    for(int i = 0; i < (int)GT[nod].size(); i++)
    {
        int vecin = GT[nod][i];
        if(Use[vecin] == 1)
        {
            DFS2(vecin);
        }
    }
}

void DFS1(int nod)
{
    Use[nod] = 1;
    for(int i = 0; i < (int)G[nod].size(); i++)
    {
        int vecin = G[nod][i];
        if(Use[vecin] == 0)
        {
            DFS1(vecin);
        }
    }
    x[++nr] = nod;
}

void Solve()
{
    for(int i = 1; i <= n; i++)
    {
        if(Use[i] == 0) DFS1(i);
    }
    for(int i = n; i >= 1; i--)
    {
        if(Use[x[i]] == 1)
        {
            nrctc++;
            DFS2(x[i]);
        }
    }
}

void Print()
{
    g<<nrctc<<'\n';
    for(int i = 1; i <= nrctc; i++)
    {
        for(int j = 0; j < (int)sol[i].size(); j++)
        {
            g<<sol[i][j]<<' ';
        }
        g<<'\n';
    }
}

int main()
{
    Read();
    Solve();
    Print();
    return 0;
}