#include <fstream>
#include <vector>
#define NMAX 100005

using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");

int i, n, m, x, y, ans = 0;
bool pl[NMAX], mi[NMAX], used[NMAX];
vector < int > v[2 * NMAX], vt[2 * NMAX], sol[NMAX];

void DFS1(int node)
{
    pl[node] = 1;

    for (auto & it : v[node])
        if (!used[it] && !pl[it])
            DFS1(it);
}

void DFS2(int node)
{
    mi[node] = 1;

    for (auto & it : vt[node])
        if (!used[it] && !mi[it])
            DFS2(it);
}

int main()
{
    f >> n >> m;

    for (i = 1; i <= m; ++ i)
    {
        f >> x >> y;

        v[x].push_back(y);
        vt[y].push_back(x);
    }

    for (i = 1; i <= n; ++ i)
        if (!used[i])
    {
        ans ++;

        for (int j = 1; j <= n; ++ j)
            pl[j] = mi[j] = 0;

        DFS1(i);
        DFS2(i);

        for (int j = 1; j <= n; ++ j)
            if (pl[j] && mi[j])
        {
            sol[ans].push_back(j);
            used[j] = 1;
        }
    }

    g << ans << '\n';

    for (i = 1; i <= ans; ++ i)
    {
        for (auto & it : sol[i])
            g << it << " ";
        g << '\n';
    }
    return 0;
}