#include <bits/stdc++.h>

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

vector<vector<int>> G, GT;

int n, m, contor;

vector<bool> V;
vector<int> S;
vector<vector<int>> CTC;

void read()
{
    fin >> n >> m;
    G = GT = vector<vector<int>>(n + 1);
    for (int i = 1; i <= m; i++)
    {
        int a, b;
        fin >> a >> b;
        G[a].push_back(b);
        GT[b].push_back(a);
    }
}

void dfs(int k)
{
    V[k] = true;
    for (auto x : G[k])
        if (!V[x])
            dfs(x);
    S.push_back(k);
}

void dfsGT(int k, vector<int> &componenta)
{
    V[k] = true;
    componenta.push_back(k);
    for (auto x : GT[k])
        if (!V[x])
            dfsGT(x, componenta);
}

int main()
{
    read();

    V = vector<bool>(n + 1, false);
    for (int i = 1; i <= n; i++)
        if (!V[i])
            dfs(i);

    V = vector<bool>(n + 1, false);
    for (vector<int>::reverse_iterator it = S.rbegin(); it != S.rend(); it++)
        if (!V[*it])
        {
            contor++;
            vector<int> componenta;
            dfsGT(*it, componenta);
            CTC.push_back(componenta);
        }

    fout << contor << "\n";
    for (const auto &componenta : CTC)
    {
        for (const auto &nod : componenta)
            fout << nod << " ";
        fout << "\n";
    }
    return 0;
}