#include <cstdio>
#include <vector>
#include <stack>
#include <algorithm>

#define N 100003

using namespace std;

int n;
int nr;
int fol[N];
int minim[N];
bool viz[N];

vector < int > g[N];
vector < int > comp;
vector < vector < int > > ctc;
stack < int > s;

void citire()
{
    freopen ("ctc.in", "r", stdin);

    int m;
    scanf ("%d %d ", &n, &m);

    while (m --)
    {
        int x;
        int y;

        scanf ("%d %d ", &x, &y);
        g[x].push_back (y);
    }
}

void tarjan(int v)
{
    s.push (v);
    viz[v] = 1;
    ++ nr;
    fol[v] = minim[v] = nr;

    unsigned int m = g[v].size();
    for (unsigned int i = 0; i < m; ++ i)
    {
        int vf = g[v][i];
        if (fol[vf] == 0)
        {
            tarjan (vf);
            minim[v] = min (minim[v], minim[vf]);
        }
        else if (viz[vf])
            minim[v] = min (minim[v], minim[vf]);
    }

    if (fol[v] == minim[v])
    {
        comp.clear();
        int nod;
        do
        {
            nod = s.top();
            s.pop();
            viz[nod] = 0;
            comp.push_back (nod);
        }
        while (nod != v);
        ctc.push_back (comp);
    }
}

void solve()
{
    for (int i = 1; i <= n; ++ i)
        if (fol[i] == 0)
            tarjan (i);
}

void afisare()
{
    freopen ("ctc.out", "w", stdout);

    unsigned int nr_ctc = ctc.size();
    printf ("%u\n", nr_ctc);

    for (unsigned int i = 0; i < nr_ctc; ++ i)
    {
        unsigned int m = ctc[i].size();
        for (unsigned int j = 0; j < m; ++ j)
            printf ("%d ", ctc[i][j]);
        printf ("\n");
    }
}

int main()
{
    citire();
    solve();
    afisare();
    return 0;
}