#include <fstream>
#include <algorithm>
#include <cmath>
#include <vector>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int n, m, i, j, x, y, mx;
vector <vector <int>> v, vt, ctct;
vector <int> viz, ord, ctc;
bool comp(vector <int> a, vector <int> b)
{
    return a[0] < b[0];
}
void dfs(int k)
{
    viz[k] = 1;
    for (int i = 0; i < v[k].size(); i++)
    {
        if (viz[v[k][i]] == 0)
        {
            dfs(v[k][i]);
        }
    }
    ord.push_back(k);
}
void dfst(int k)
{
    ctc[k] = j;
    for (int i = 0; i < vt[k].size(); i++)
    {
        if (ctc[vt[k][i]] == 0)
        {
            dfst(vt[k][i]);
        }
    }
}
int main()
{
    fin >> n >> m; v.resize(n + 1); vt.resize(n + 1), viz.resize(n + 1); ctc.resize(n + 1);
    for (i = 1; i <= m; i++)
    {
        fin >> x >> y;
        v[x].push_back(y);
        vt[y].push_back(x);
    }
    for (i = 1; i <= n; i++)
        if (viz[i] == 0) dfs(i);
    for (i = n - 1; i >= 0; i--)
    {
        if (ctc[ord[i]] == 0)
        {
            j++;
            dfst(ord[i]);
        }
    }
    fout << j << "\n";
    ctct.resize(j);
    for (i = 1; i <= n; i++)
        ctct[ctc[i] - 1].push_back(i);
    for (i = 0; i < ctct.size(); i++)
    {
        for (x = 0; x < ctct[i].size(); x++)
            fout << ctct[i][x] << " ";
        fout << "\n";
    }
    return 0;
}