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

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

const int Nmax = 100005;
vector <int> G[Nmax] ,GT[Nmax], sol[Nmax];

int n, m, use[Nmax],nr, x[Nmax],k;

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]) DFS1(vecin);
    }
    x[++k] = nod;
}

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

int main()
{
    f>>n>>m;
    for(int i = 1; i <= m; i++)
    {
        int x,y;
        f>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    for(int i = 1; i <= n; i++)
    {
        if(use[i] == 0) DFS1(i);
    }
    for(int i = n; i > 0; i--)
    {
        if(use[x[i]] == 1)
        {
            nr++;
            DFS2(x[i]);
        }
    }
    g<<nr<<'\n';
    for(int i = 1; i <= nr; i++)
    {
        for(int j = 0; j < (int)sol[i].size(); j++)
            g<<sol[i][j]<<' ';
        g<<'\n';
    }
    return 0;
}