#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
#include <deque>

using namespace std;

#define maxN 100005
#define PB push_back

vector <int> List[maxN], ListT[maxN], Sol[maxN];
deque <int> Q;
bool Viz[maxN];
int N, M, comp;


void DFP (int nod)
{
    Viz[nod] = true;

    for (unsigned int i = 0; i < List[nod].size(); ++ i)
    {
        int nod2 = List[nod][i];

        if (Viz[nod2]) continue;

        DFP (nod2);
    }

    Q.PB (nod);
}


void DFM (int nod)
{
    Viz[nod] = true;
    Sol[comp].PB (nod);

    for (unsigned int i = 0; i < ListT[nod].size(); ++ i)
    {
        int nod2 = ListT[nod][i];

        if (Viz[nod2]) continue;

        DFM (nod2);
    }
}


void Kosaraju ()
{
    for (int i = 1; i <= N; ++ i)
    {
        if (Viz[i]) continue;
        DFP (i);
    }

    memset (Viz, false, sizeof (Viz));

    for (int i = Q.size() - 1; i >= 0; -- i)
    {
        if (Viz[Q[i]]) continue;

        ++ comp;
        DFM (Q[i]);
    }
}


int main()
{
    freopen ("ctc.in", "r", stdin);
    freopen ("ctc.out", "w", stdout);

    scanf ("%d %d", &N, &M);

    while (M --)
    {
        int x, y;
        scanf ("%d %d", &x, &y);

        List[x].PB (y);
        ListT[y].PB (x);
    }

    Kosaraju ();

    printf ("%d\n", comp);
    for (int i = 1; i <= comp; ++ i)
    {
        for (int j = 0; j < Sol[i].size(); ++ j) printf ("%d ", Sol[i][j]);
        printf ("\n");
    }

    return 0;
}