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

using namespace std;

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

int i, n, m, x, y, cnt = 0, start[NMAX], anscnt;
bool visited[NMAX];

vector < int > v[NMAX], ans[NMAX], vt[NMAX];

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

    for (vector < int > :: iterator it = v[node].begin(); it != v[node].end(); ++ it)
        if (!visited[*it])
            DFS1(*it);

    start[++ cnt] = node;
}

void DFS2(int node)
{
    visited[node] = 0;
    ans[anscnt].push_back(node);

    for (vector < int > :: iterator it = vt[node].begin(); it != vt[node].end(); ++ it)
        if (visited[*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 (!visited[i])
            DFS1(i);

    for (i = cnt; i >= 1; -- i)
        if (visited[start[i]])
        {
            anscnt ++;
            DFS2(start[i]);
        }

    g << anscnt << '\n';

    for (i = 1; i <= anscnt; ++ i)
    {
        for (vector < int > :: iterator it = ans[i].begin(); it != ans[i].end(); ++ it)
            g << *it << " ";
        g << '\n';
    }
    return 0;
}