#include <bits/stdc++.h>

using namespace std;

ifstream f ("ctc.in");
ofstream g ("ctc.out");

vector <int> G1[100002];
vector <int> G2[100002];
vector <int> st;
vector <int> ctc[100002];

int n, m, x, y, nrc;

bool viz1[100002], viz2[100002];

void dfs1 (int nod)
{
    vector <int> :: iterator it;
    viz1[nod] = true;

    for (it = G1[nod].begin(); it != G1[nod].end(); it++)
    {
        if (!viz1[*it])
        {
            dfs1(*it);
        }
    }
    st.push_back(nod);
}
void dfs2 (int nod)
{
    vector <int> :: iterator it;
    viz2[nod] = true;

    for (it = G2[nod].begin(); it != G2[nod].end(); it++)
    {
        if (!viz2[*it])
        {
            dfs2(*it);
        }
    }
    ctc[nrc].push_back(nod);
}
int main()
{
    f >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        f >> x >> y;
        G1[x].push_back(y);
        G2[y].push_back(x);
    }

    for (int i = 1; i <= n; i++)
    {
        if (!viz1[i])
        {
            dfs1(i);
        }
    }

    reverse(st.begin(),st.end());

    for (int i = 0; i < n; i++)
    {
        if (!viz2[st[i]])
        {
            nrc++;
            dfs2(st[i]);
        }
    }

    g << nrc << '\n';

    for (int i = 1; i <= nrc; i++)
    {
        vector <int> :: iterator it;
        for (it = ctc[i].begin(); it != ctc[i].end(); it++)
        {
            g << *it << " ";
        }
        g << '\n';
    }
    return 0;
}