#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];
void Tarjan(int nod,int cnt)
{
    //cout << nod<< endl;
    for(auto x:adiacenta[nod])
    {
        if(!viz[x])
        {
            st.push(x);
            in_stack[x] = 1;
            viz[x] = 1;
            low_link[x] = cnt;
            indice[x] = cnt;
            Tarjan(x,cnt+1);
        }
    }
    for(auto x:adiacenta[nod])
    {
        if(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();
    st.push(1);
    in_stack[1] = 1;
    viz[1] = 1;
    Tarjan(1,1);
    afisare();
}