#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
#include <algorithm>

using namespace std;

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

const int maxN = 100005;
int n, m, nrctc;
vector <int> G[maxN], Gback[maxN], ord, comp[maxN];
bool used[maxN];

void dfs1(int nod)
{
    used[nod] = 1;
    for(int vecin : G[nod])
        if(!used[vecin])
            dfs1(vecin);
    ord.push_back(nod);
}

void dfs2(int nod)
{
    used[nod] = 1;
    comp[nrctc].push_back(nod);
    for(int vecin : Gback[nod])
        if(!used[vecin])
            dfs2(vecin);
}

int main()
{
    fin >> n >> m;
    for(int x, y, i = 1; i <= m; i++)
    {
        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;
    reverse(ord.begin(), ord.end());
    for(int x : ord)
    {
        if(!used[x])
        {
            nrctc++;
            dfs2(x);
        }
    }
    fout << nrctc << '\n';
    for(int i = 1; i <= nrctc; i++)
    {
        for(int x : comp[i])
            fout << x << ' ';
        fout << '\n';
    }
    return 0;
}