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

    if(id[nod] == low_link[nod])
    {
        while(1)
        {
            int curent = st.top();
            in_stack[curent] = 0;
            rasp_temp.push_back(curent);
            st.pop();
            if(id[curent] == low_link[curent])
                break;
        }
        comp_cnt++;
        rasp[comp_cnt] = rasp_temp;
        rasp_temp.clear();
    }

}
void citire()
{
    f >> n >> m;
    int x,y;
    for(int i = 1; i<=m; i++)
    {
        f >> x >> y;
        adiacenta[x].push_back(y);
    }
}
void afisare()
{
    g << comp_cnt<<endl;
    for(int i = 1;i<=comp_cnt;i++)
    {
        for(auto x:rasp[i])
            g << x<< " ";
        g << endl;
    }
}
int main()
{
    citire();
    for(int i = 1; i<=n; i++)
        if(!viz[i])
            {
                in_stack[i] = 1;
                st.push(i);
                Tarjan_alg(i);
            }
    afisare();
}