#include <bits/stdc++.h>
#define nmax 100005

using namespace std;

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

vector < int > L[nmax];
vector < int > T[nmax];
vector < int > sol[nmax];
int n, m, nrc;
bitset < nmax > viz;
stack < int > st;

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

void Dfs1(int k)
{
    viz[k] = 1;
    for(auto i : L[k])
        if(viz[i] == 0)
            Dfs1(i);
    st.push(k);
}

void Dfs2(int k)
{
    viz[k] = 1;
    sol[nrc].push_back(k);
    for(auto i : T[k])
        if(viz[i] == 0)
            Dfs2(i);
}

void CTC()
{
    int i, k;
    for(i = 1; i <= n; i++)
        if(viz[i] == 0) Dfs1(i);
    viz.reset();
    while(!st.empty())
    {
        k = st.top();
        st.pop();
        if(viz[k] == 0)
        {
            nrc++;
            Dfs2(k);
        }
    }
}

void Afisare()
{
    fout << nrc << "\n";
    for(int i = 1; i <= nrc; i++, fout << "\n")
        for(auto j : sol[i])
            fout << j << " ";
}

int main()
{
    Citire();
    CTC();
    Afisare();
    return 0;
}