#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
using namespace std;

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

vector<int> vecini[100004];
vector<int> veciniT[100005];
vector<int> CompConex[100005];
vector<int> S;
int n,m,nrComp;
int a,b;
bool viz[100005];
void resetare()
{
    for(int i=1; i<=n; i++)viz[i]=false;
}

void DFS(int curent)
{
    viz[curent]=true;

    for(int v:vecini[curent])
        if(viz[v]==false)
            DFS(v);

    S.push_back(curent);

}

void DFST(int curent)
{

    viz[curent]=true;
    CompConex[nrComp].push_back(curent);

    for(int v:veciniT[curent])
        if(viz[v]==false)
            DFST(v);


}
int main()
{
    fi>>n>>m;
    for(int i=1; i<=m; i++)
    {
        fi>>a>>b;
        vecini[a].push_back(b);
        veciniT[b].push_back(a);
    }

    for(int i=1; i<=n; i++) if(viz[i]==false) DFS(i);

    resetare();

    for(int C: S)
        {

        if(viz[C]==false)
        {
            nrComp++;
            DFST(C);
        }
    }

    fo<<nrComp<<'\n';
    for(int i=1; i<=nrComp; i++)
    {
        if(CompConex[i].empty()==false)
        {
            for(auto x:CompConex[i])
                fo<<x<<" ";
            fo<<'\n';
        }

    }
    fi.close();
    fo.close();
    return 0;
}