#include <bits/stdc++.h>
using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

int n, m, viz[100003], v[100003], len, nrctc;
vector<int> l[100003], g[100003];

void Citire()
{
    int i, j, p;
    fin >> n >> m;
    for (p = 1; p <= m; p++)
    {
        fin >> i >> j;
        l[i].push_back(j);
        g[j].push_back(i);
    }
}
void DFS_TF(int x)
{
    viz[x] = 1;
    for (int i : l[x])
        if (viz[i] == 0) DFS_TF(i);
    v[++len] = x;
}

void SortTop()
{
    for (int i = 1; i <= n; i++)
        if (viz[i] == 0) DFS_TF(i);
}

void DFS(int x)
{
    viz[x] = nrctc;
    for (int i : g[x])
        if (viz[i] == 0) DFS(i);
}

void Kosaraju()
{
    int i, j, k;
    SortTop();
    for (i = 1; i <= n; i++)
        viz[i] = 0;
    for (i = n; i >= 1; i--)
    {
        k = v[i];
        if (viz[k] == 0)
        {
            nrctc++;
            DFS(k);
        }
    }
    fout << nrctc << "\n";
    for (i = 1; i <= nrctc; i++)
    {
        for (j = 1; j <= n; j++)
            if (viz[j] == i) fout << j << " ";
        fout << "\n";
    }
}

int main()
{
    ios_base::sync_with_stdio(0);
    fin.tie(0);
    fout.tie(0);
    Citire();
    Kosaraju();
    return 0;
}


//0, 1, 3-5, 7-18, 21, 22, 24-27, 29, 30, 34-36, 42, 44, 45, 47, 48, 51, 54, 56-58