#include <iostream>
#include <fstream>
#include <vector>
#define nmax 100005
using namespace std;
vector<int> vec[nmax],invec[nmax];//out-neighbour; in-noughbour
int n,m,viz[nmax],L[nmax],k,comp[nmax],NrComp;
void citire()
{
    int x,y;
    scanf("%d%d",&n,&m);
    for(int i=1; i<=m; i++)
    {
        scanf("%d%d",&x,&y);
        vec[x].push_back(y);
        invec[y].push_back(x);
    }
}

void vizitare(int u)
{
    if(viz[u])
        return;

    viz[u]=1;
    for(int i=0;i<vec[n].size();i++)
            vizitare(vec[n][i]);
    L[++k] = u;
}

void creazaComponenta(int u)
{
    if(comp[u])
        return;

    /*if(u==rad)
    comp[u]=++comp[0];*/

    comp[u]=NrComp;
    for(int i=0; i<invec[u].size(); i++)
            creazaComponenta(invec[u][i]);
}

int main()
{
    freopen("ctc.in","rt",stdin);
    freopen("ctc.out","wt",stdout);
    citire();
    for(int u=1; u<=n; u++)
        vizitare(u);

    while(k>0)
    {
        if(comp[L[k]]==0)
        {
            NrComp++;
            creazaComponenta(L[k]);
        }
        k--;
    }


    cout<<NrComp<<'\n';
    for(int i=1; i<=NrComp; i++)
    {
        for(int j=1; j<=n; j++)
            if(comp[j]==i)
                cout<<j<<' ';
            cout<<'\n';
    }
    return 0;
}