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

using namespace std;

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

int i, n, m, x, y, start[NMAX], cont = 0;
vector < int > v[NMAX], vt[NMAX], sol[NMAX];
bool used[NMAX];

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

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

    start[++ cont] = node;
}

void DFS2(int node)
{
    used[node] = 0;
    sol[cont].push_back(node);

    for (auto & it : vt[node])
        if (used[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])
            DFS1(i);

    cont = 0;

    for (i = n; i >= 1; -- i)
        if (used[start[i]])
    {
        cont ++;
        DFS2(start[i]);
    }

    g << cont << '\n';

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