#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#include <queue>
using namespace std;
ifstream f("ctc.in");
ofstream g ("ctc.out");
vector<int>adiacenta[100001];
vector<int>rasp[100001];
stack<int>st;
int comp,cnt;
int viz[100001];
int dist[100001];
int n,m;
bool in_stack[100001];
int indice[100001];
int low_link[100001];
void citire()
{
    f >> n >> m;
    for(int i = 1; i<=m; i++)
    {
        int x,y,c;
        f >> x>> y;
        adiacenta[x].push_back(y);
    }
}
void DFS(int nod)
{
    viz[nod] = 1;
    low_link[nod]=++cnt;
    indice[nod] = cnt;
    in_stack[nod]=1;
    st.push(nod);
    for(auto x:adiacenta[nod])
    {
        if(!viz[x])
        {
            DFS(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])
    {
        comp++;
        while(!st.empty())
        {
            int curent = st.top();
            st.pop();
            rasp[comp].push_back(curent);
            in_stack[curent]=0;
            if(low_link[curent]==indice[curent])
                break;
        }
    }
}
int main()
{
    citire();
    for(int i =1; i<=n; i++)
    {
        if(!viz[i])
            DFS(i);
    }
    g << comp<<'\n';
    for(int i = 1; i<=comp; i++)
    {
        for(auto x:rasp[i])
            g << x<< " ";
        g << '\n';
    }

}