#include <bits/stdc++.h>

using namespace std;

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

vector<int> L[100005];
vector<int> T[100005];
vector<int> Comp[100005];
stack<int> st;
int n, k, nrc;
int viz[100005];

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

void Dfs(int nod)
{
    viz[nod] = 1;
    for(auto e : L[nod])
        if(!viz[e]) Dfs(e);
    st.push(nod);
}

void SortTop()
{
    for(int i = 1; i <= n; i++)
        if(!viz[i]) Dfs(i);
}

void Dfs2(int nod)
{
    viz[nod] = nrc;
    Comp[nrc].push_back(nod);
    for(auto e : T[nod])
        if(!viz[e]) Dfs2(e);
}

void Rezolvare()
{
    int nod;
    for(int i = 1; i <= n; i++)
         viz[i] = 0;
    nrc = 0;
    while(!st.empty())
    {
        nod = st.top();
        st.pop();
        if(!viz[nod])
        {
            nrc++;
            Dfs2(nod);
        }
    }
    fout << nrc << "\n";
    for(int i = 1; i <= nrc; i++)
    {
        for(auto e : Comp[i])
            fout << e << " ";
        fout << "\n";
    }
}

int main()
{
    Citire();
    SortTop();
    Rezolvare();
    fin.close();
    fout.close();
    return 0;
}