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

using namespace std;

const int nmx = 100002;

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

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

void dfs(int nod)
{
    viz[nod] = true;

    for(vector<int>::iterator it = g[nod].begin(); it != g[nod].end(); ++it)
        if(not viz[*it])
            dfs(*it);

    srt.push_back(nod);
}

void dfs2(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])
            dfs2(*it);
}

void afish()
{
    int l = rasp.size();

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

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

    citire();
    for(int i = 1; i <= n; ++i)
        if(not viz[i])
            dfs(i);

    viz.reset();

    for(vector<int>::reverse_iterator it = srt.rbegin(); it != srt.rend(); ++it)
        if(not viz[*it])
        {
            aux.clear();
            dfs2(*it);
            rasp.push_back(aux);
        }
    afish();

    return 0;
}