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

using namespace std;

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

vector <int> L[N];
vector <int> T[N];
vector <int> sol[N];
stack <int> st;
bitset <N> viz;

int n, m, nrcc;

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

void DFS2(int nod)
{
    viz[nod] = 1;
    sol[nrcc].push_back(nod);
    for(auto i : T[nod])
        if(viz[i] == 0)
            DFS2(i);
}

void DFS1(int nod)
{
    viz[nod] = 1;
    for(auto i : L[nod])
        if(viz[i] == 0)
            DFS1(i);
    st.push(nod);
}

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)
        {
            nrcc++;
            DFS2(k);
        }
    }
}

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

int main()
{
    Read();
    CTC();
    Write();
    return 0;
}