#include <bits/stdc++.h>
#define Dmax 100005
using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");
vector <int>G[Dmax],GT[Dmax],CTC[Dmax];
stack <int> S;
int viz[Dmax];
int N,M,NRC;
void citire()
{
    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);
    }
}
void DFS1(int v)
{
    viz[v]=1;
    for(unsigned int i=0; i<G[v].size(); i++)
    {
        int Vecin = G[v][i];
        if(!viz[Vecin])
            DFS1(Vecin);
    }
    S.push(v);
}
void DFS2(int v)
{
    viz[v]=2;
    CTC[NRC].push_back(v);
    for(unsigned int i=0; i<GT[v].size(); i++)
    {
        int Vecin = GT[v][i];
        if(viz[Vecin]==1)
            DFS2(Vecin);
    }
}
void Kosaraju()
{
    for(int i=1;i<=N;i++)
        if(!viz[i])
        DFS1(i);

    while(!S.empty())
    {
        int Nod = S.top();
        if(viz[Nod]==1)
        {
            NRC++;
            DFS2(Nod);
        }
        S.pop();
    }

}
void afisare()
{
    cout<<NRC<<"\n";
    for(int i=1; i<=NRC;i++)
    {
        for(unsigned int j=0; j<CTC[i].size(); j++)
            g<<CTC[i][j]<<" ";
        g<<"\n";
    }

}
int main()
{
    citire();
    Kosaraju();
    afisare();

    return 0;
}