#include <bits/stdc++.h>

using namespace std;

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

vector <int> l[100001];
vector <int> t[100001];
vector <int> sol[100001];
bitset <100001> viz;
stack <int> st;
int n, m, nrc;

void citire()
{
    int i, x, y;
    fin >> n >> m;
    for(i = 1 ; i <= m ; i++)
    {
        fin >> x >> y;
        l[x].push_back(y);
        t[y].push_back(x);
    }
}

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()
{
    for(int i = 1 ; i <= n ; i++)
        if(viz[i] == 0)
            dfs1(i);
    viz.reset();
    int nod;
    while(!st.empty())
    {
        nod = st.top();
        st.pop();
        if(viz[nod] == 0)
        {
            nrc++;
            dfs2(nod);
        }
    }
    fout << nrc << endl;
    for(int i = 1 ; i <= n ; i++)
    {
        for(auto k : sol[i])
            fout << k << " ";
        fout << "\n";
    }

}

int main()
{
    citire();
    ctc();

    fin.close();
    fout.close();
    return 0;
}