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

//Rezolvare: algoritmul lui Kosaraju

using namespace std;

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

int n, m;
vector <int> l[100001], li[100001], ctc[100001];
int viz[100001], inc, nr;
stack <int> st; //stiva in care adaugam nodurile dupa dfs

void dfs(int nod)
{
    viz[nod]=1;
    for(int i=0; i<l[nod].size(); i++)
    {
        if(viz[l[nod][i]]==0)
        {
            dfs(l[nod][i]);
        }
    }
    st.push(nod); //adaugam in stiva nodul curent dupa ce i-am parcurs urmasii in dfs
}

void dfsi(int nod, int nr) //dfs pt graful invers
{
    viz[nod]=2; //e viz in dfs invers
    ctc[nr].push_back(nod); //adaug nodul in ctc curenta (nr)
    for(int i=0; i<li[nod].size(); i++)
    {
        if(viz[li[nod][i]]==1) //daca e deja vizitat dupa dfs
        {
            dfsi(li[nod][i], nr);
        }

    }


}

int main()
{
    in>>n>>m;
    int x, y;
    for(int i=1; i<=m; i++)
    {
        in>>x>>y;
        l[x].push_back(y); //adaugam in lista de adiacenta
        li[y].push_back(x); //adaugam in lista de adiacenta a grafului invers
    }

    for(int i=1; i<=n; i++)
    {
        if(viz[i]==0)
            dfs(i);
    }

    while(st.empty()==false)
    {
        int crt=st.top(); //ultimul elem pus in stiva dupa dfs
        if(viz[crt]==1)
        {
            nr++; //creste nr de componente conexe (nodul crt nu e in ctc curenta)
            dfsi(crt, nr);
        }
        st.pop(); //scot elem crt din stiva

    }

    out<<nr<<"\n";
    for(int i=1; i<=nr; i++)
    {
        for(int j=0; j<ctc[i].size(); j++)
            out<<ctc[i][j]<<" ";
        out<<"\n";
    }

    return 0;
}