#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

const string filename = "ctc";
ifstream fin(filename + ".in");
ofstream fout(filename + ".out");

int n, m, cc;
bool used[100005];
vector <int> ordine, componenta[100005];
vector <int> G[100005], Gback[100005];

void dfs1(int nod)
{
    used[nod] = true;
    for(int vecin : G[nod])
        if(!used[vecin])
            dfs1(vecin);
    ordine.push_back(nod);
}

void dfs2(int nod)
{
    used[nod] = true;
    componenta[cc].push_back(nod);
    for(int vecin : Gback[nod])
        if(!used[vecin])
            dfs2(vecin);
}

int main()
{
    fin >> n >> m;
    for(int i = 1; i <= m; i++)
    {
        int x, y;
        fin >> x >> y;
        G[x].push_back(y);
        Gback[y].push_back(x);
    }
    for(int i = 1; i <= n; i++)
        if(!used[i])
            dfs1(i);
    for(int i = 1; i <= n; i++)
        used[i] = 0;
    for(int i = ordine.size() - 1; i >= 0; i--)
    {
        int nod = ordine[i];
        if(!used[nod])
        {
            cc++;
            dfs2(nod);
        }
    }
    fout << cc << '\n';
    for(int i = 1; i <= cc; i++)
    {
        for(int elem : componenta[i])
            fout << elem << ' ';
        fout << '\n';
    }
}