#include <bits/stdc++.h>
using namespace std;

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

int n, m;
int comp[100005];
bitset<100005> viz;
vector<int> L[100005], T[100005];
stack<int> st;

void DFS(int k)
{
    viz[k] = 1;
    for (int i : L[k])
        if (viz[i] == 0)
            DFS(i);
    st.push(k);
}
void DFST(int k)
{
    comp[k] = m;
    for (int i : T[k])
        if (comp[i] == 0)
            DFST(i);
}

int main()
{
    int i, j;
    fin >> n >> m;
    while (m--)
    {
        fin >> i >> j;
        L[i].push_back(j);
        T[j].push_back(i);
    }

    for (i = 1; i <= n; i++)
        if (viz[i] == 0)
            DFS(i);

    m = 0;
    while (!st.empty())
    {
        i = st.top();
        st.pop();
        if (comp[i] == 0)
        {
            m++;
            DFST(i);
        }
    }

    fout << m << "\n";
    for (i = 1; i <= m; i++)
    {
        for (j = 1; j <= n; j++)
            if (comp[j] == i)
                fout << j << " ";
        fout << "\n";
    }
    return 0;
}