#include <fstream>
#include <vector>
#define NMax 100005
using namespace std;

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

int N,M,Sol,Use[NMax],O[NMax],k;
vector <int> G[NMax], GT[NMax],CTC[NMax];

void Read()
{
    fin>>N>>M;
    for(int i=1;i<=M;i++)
        {
            int x,y;
            fin>>x>>y;
            G[x].push_back(y);
            GT[y].push_back(x);
        }
}
void DFSP(int Node)
{
    Use[Node] = 1;
    for(int i=0; i< (int)G[Node].size(); i++)
        {
            int Vecin = G[Node][i];
            if(Use[Vecin]==0)
                DFSP(Vecin);
        }
    O[++k] = Node;
}

void DFSM(int Node)
{
    Use[Node] = 2; CTC[Sol].push_back(Node);
    for(int i=0; i< (int)GT[Node].size(); i++)
        {
            int Vecin = GT[Node][i];
            if(Use[Vecin]==1)
                DFSM(Vecin);
        }
}

void Solve()
{
    for(int i=1;i<=N; i++)
        if(!Use[i])
            DFSP(i);

    for(int i=N;i>=1; i--)
        {
            if(Use[O[i]]==1)
            {
                Sol++;

                DFSM(O[i]);
            }
        }
}

void Print()
{
    fout<<Sol<<"\n";
    for(int i=1;i<=Sol;i++)
        {
            for(int j = 0; j< (int) CTC[i].size();j++)
                fout<<CTC[i][j]<<" ";
            fout<<"\n";
        }
}

int main()
{
    Read();
    Solve();
    Print();
    return 0;
}