#include <iostream>
#include <fstream>
#include<stack>
#include <vector>
using namespace std;
ifstream f("ctc.in");
ofstream g ("ctc.out");
int n,m,cnt_rasp;
vector<int>adiacenta[100001];
stack<int>st;
vector<int>rasp;
vector<int>rasp_final[100001];
bool in_stack[100001];
int indice[100001],low_link[100001],cnt;
bool viz[100001];
//explicatie https://www.youtube.com/watch?v=TyWtx7q2D7Y&ab_channel=WilliamFiset
void Tarjan(int nod)
{
    for(auto x:adiacenta[nod])
    {
        if(!viz[x])
        {
            st.push(x);
            in_stack[x] = 1;
            viz[x] = 1;
            cnt++;
            low_link[x] = cnt;
            indice[x] = cnt;
            Tarjan(x);
        }
    }
    for(auto x:adiacenta[nod])
    {
        if(viz[x] && in_stack[x])
            low_link[nod] = min(low_link[nod],low_link[x]);
    }

    if(low_link[nod] == indice[nod])
    {
        while(1)
        {
            int curent = st.top();
            in_stack[curent] = 0;
            rasp.push_back(curent);
            st.pop();

            if(indice[curent] == low_link[curent])
                break;

        }
        rasp_final[cnt_rasp++]=rasp;
        rasp.clear();
    }

}
void afisare()
{
    g << cnt_rasp<< endl;
    for(int i = 0; i<cnt_rasp; i++)
    {
        for(int j = 0; j<rasp_final[i].size(); j++)
        {
            g << rasp_final[i][j]<< " ";
        }
        g <<'\n';
    }
}
void citire()
{
    f >> n >> m;
    for(int i = 1; i<=m; i++)
    {
        int x,y;
        f >> x >> y;
        adiacenta[x].push_back(y);
    }
}
int main()
{
    citire();


    for(int i = 1; i<=n; i++)
    {
        if(!viz[i])
        {
            st.push(i);
            in_stack[i] = 1;
            cnt++;
            indice[i] = low_link[i] = cnt;
            viz[i] = 1;
            Tarjan(i);
        }
    }
    afisare();
}