#include <iostream>
#include <fstream>
#include <vector>
#define nmax 100005
using namespace std;
vector<int> vec[nmax],invec[nmax],L,Sol[nmax];//out-neighbour; in-noughbour
int n,m,viz[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[u].size();++i)
            vizitare(vec[u][i]);
    L.push_back(u);
}

void creazaComponenta(int u,int componenta)
{
    comp[u]=componenta;
    Sol[componenta].push_back(u);
    for(int i=0; i<invec[u].size(); ++i)
    {
        int nod=invec[u][i];
        if(!comp[nod])
            creazaComponenta(nod,componenta);
    }
}

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

    while(L.size())
    {
        if(comp[L.back()]==0)
            creazaComponenta(L.back(),++NrComp);
        L.pop_back();
    }

    cout<<NrComp<<'\n';
    for(int i=1; i<=NrComp; i++)
    {
        for(int j=0; j<Sol[i].size(); j++)
            cout<<Sol[i][j]<<' ';
            cout<<'\n';
    }
}