#include <algorithm>
#include <iostream>
#include <fstream>
#include <bitset>
#include <vector>
#include <stack>
#include <list>
using namespace std;
ifstream fin ("ctc.in");
ofstream fout("ctc.out");
#define NMAX 100002
vector<int> G[NMAX], GT[NMAX];
int n, m;
vector<vector<int>> ctc;
int index[NMAX], index2[NMAX], cindex, cindex2;
bitset<NMAX> vis1, vis2;
stack<int> stk;

void dfs1(int i, int c)
{
    vis1[i] = true;
    index[i] = c;
    for (int const& v : G[i])
    {
        if (!vis1[v])
            dfs1(v, c);
    }
    stk.push(i);
}

void dfs2(int i, int c)
{
    vis2[i] = true;
    index2[i] = c;
    for (int const& v : GT[i])
        if (!vis2[v])
            dfs2(v, c);
}

void kosaraju()
{
    for (int i = 1; i <= n; i++)
        if (!vis1[i])
            dfs1(i, ++cindex);

    while (!stk.empty())
    {
        int x = stk.top();
        stk.pop();

        if (!vis2[x])
            dfs2(x, ++cindex2);
    }

    ctc.clear();
    ctc.resize(cindex2);

    for (int i=1; i<=n; i++)
    {
        ctc[index2[i]-1].push_back(i);
    }
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    fin>>n>>m;

    for (int i = 0; i < m; i++)
    {
        int a, b;
        fin >> a >> b;
        G[a].push_back(b);
        GT[b].push_back(a);
    }

    kosaraju();

    fout << ctc.size() << '\n';
    for (auto & cc : ctc)
    {
        for (auto & x : cc)
            fout << x << ' ';
        fout << '\n';
    }

    return 0;
}