#include <cstdio>
#include <vector>
#include <bitset>

using namespace std;

const int nmx = 100002;

int n,m,srt[nmx];
vector <int> g1[nmx], g2[nmx], aux;
bitset <nmx> viz;
vector <vector<int> > ans;

void citire()
{
    scanf("%d %d", &n, &m);
    for(int i = 1; i <= m; ++i)
    {
        int nod1,nod2;
        scanf("%d %d", &nod1, &nod2);
        g1[nod1].push_back(nod2);
        g2[nod2].push_back(nod1);
    }
}

void parcurgere(int nod)
{
    viz[nod] = true;
    for(vector<int>::iterator it = g1[nod].begin(); it != g1[nod].end(); ++it)
        if(not viz[*it])
            parcurgere(*it);
    srt[++srt[0]] = nod;
}

void sortaret()
{
    for(int i = 1; i <= n; ++i)
        if(not viz[i])
            parcurgere(i);
}

void invers(int nod)
{
    viz[nod] = true;
    aux.push_back(nod);
    for(vector<int>::iterator it = g2[nod].begin(); it != g2[nod].end(); ++it)
        if(not viz[*it])
            invers(*it);
}

void componente()
{
    viz.reset();
    for(int i = n; i; --i)
        if(not viz[srt[i]])
        {
            aux.clear();
            invers(srt[i]);
            ans.push_back(aux);
        }
}

void afish()
{
    printf("%d\n", ans.size());
    for(size_t i = 0; i < ans.size(); ++i)
    {
        for(size_t j = 0; j < ans[i].size(); ++j)
            printf("%d ", ans[i][j]);
        printf("\n");
    }
}

int main()
{
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    citire();
    sortaret();
    componente();
    afish();
    return 0;
}