#include <bits/stdc++.h>

using namespace std;

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

vector <int> Sol[100005];
vector <int> G1[100005];
vector <int> G2[100005];
vector <int> st;

int ntc, n, m, x, y;
bool viz1[100005], viz2[100005];
void dfs1 (int nod)
{
    viz1[nod] = true;
    for (int i = 0; i < G1[nod].size(); i++)
    {
        if (!viz1[G1[nod][i]])
        {
            dfs1(G1[nod][i]);
        }
    }
    st.push_back(nod);
}
void dfs2 (int nod)
{
    viz2[nod] = true;
    for (int i = 0; i < G2[nod].size(); i++)
    {
        if (!viz2[G2[nod][i]])
        {
            dfs2(G2[nod][i]);
        }
    }
    Sol[ntc].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]])
        {
            ntc++;
            dfs2(st[i]);
        }
    }

    g << ntc << '\n';

    for (int i = 1; i <= ntc; i++)
    {
        for (int j = 0; j < Sol[i].size(); j++)
        {
            g << Sol[i][j] << " ";
        }
        g << '\n';
    }
    return 0;
}