#include <fstream>
#include <vector>
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
int N, M;
vector <int> G[100005], GT[100005], CTC[100005];
int O[100005], k;
bool Use[100005];
int NRC;
void Read()
{
    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 DFP(int node)
{
    Use[node] = 1;
    for(int i = 0; i < G[node].size(); i++)
    {
        int neighb = G[node][i];
        if(Use[neighb] == 0)
            DFP(neighb);
    }
    O[++k] = node;
}

void DFM(int node)
{
    Use[node] = 0;
    CTC[NRC].push_back(node);
    for(int i = 0; i < GT[node].size(); i++)
    {
        int neighb = GT[node][i];
        if(Use[neighb] == 1)
            DFM(neighb);
    }
}

void Kosaraju()
{
    for(int i = 1; i <= N; i++)
        if(Use[i] == 0)
            DFP(i);
    for(int i = k; i >= 1; i--)
    {
        if(Use[O[i]] == 1)
        {
            ++NRC;
            DFM(O[i]);
        }
    }
    g << NRC << "\n";
    for(int i = 1; i <= NRC; i++)
    {
        for(int j = 0; j < CTC[i].size(); j++)
            g << CTC[i][j] << " ";
        g << "\n";
    }
}
int main()
{
    Read();
    Kosaraju();
    return 0;
}