#include <fstream>
#include <vector>
#include <stack>
using namespace std;
const int NMAX = 100003;
bool viz[NMAX];
int comp[NMAX];
vector <int> discover;
vector <int> g[NMAX], gt[NMAX];
vector <int> ans[NMAX];
void dfsplus(int nod)
{
    viz[nod] = 1;
    for (int v : g[nod])
        if (!viz[v])
            dfsplus(v);
    discover.push_back(nod);
}
int nr;
void dfsminus(int nod)
{
    comp[nod] = nr;
    for (int v : gt[nod])
        if (!comp[v])
            dfsminus(v);
}
int main()
{
    ifstream cin("ctc.in");
    ofstream cout("ctc.out");
    int n, m, i;
    cin >> n >> m;
    for (i = 1; i <= m; i++)
    {
        int a, b;
        cin >> a >> b;
        g[a].push_back(b);
        gt[b].push_back(a);
    }
    for (i = 1; i <= n; i++)
        if (!viz[i])
            dfsplus(i);
    for (i = discover.size() - 1; i > -1; i--)
        if (!comp[discover[i]])
        {
            nr++;
            dfsminus(discover[i]);
        }
    for (i = 1; i <= n; i++)
        ans[comp[i]].push_back(i);
    cout << nr << "\n";
    for (i = 1; i <= n; i++)
        if (!ans[i].empty())
        {
            for (int j = 0; j < ans[i].size(); j++)
                cout << ans[i][j] << " ";
            cout << "\n";
        }
}