#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],adiacenta1[100001];
vector<int>rasp[100001];
stack<int>st;
int comp;
int cnt[100001];
int viz[100001];
int dist[100001];
int n,m;
void citire()
{
    f >> n >> m;
    for(int i = 1; i<=m; i++)
    {
        int x,y,c;
        f >> x>> y;
        adiacenta[x].push_back(y);
        adiacenta1[y].push_back(x);
    }
}
void DFS(int nod)
{
    viz[nod] = 1;
    for(auto x:adiacenta[nod])
    {
        if(!viz[x])
        {
            DFS(x);
        }
    }
    st.push(nod);
}
void DFS1(int nod)
{
    rasp[comp].push_back(nod);
    viz[nod] = 2;
    for(auto x:adiacenta1[nod])
    {
        if(viz[x]!=2)
        {
            DFS1(x);
        }
    }
}
int main()
{
    citire();
    for(int i =1; i<=n; i++)
    {
        if(!viz[i])
            DFS(i);
    }
    while(!st.empty())
    {
        if(viz[st.top()]!=2)
        {

            comp++;
            DFS1(st.top());
        }
        st.pop();
    }
    g << comp<<'\n';
    for(int i = 1; i<=comp; i++)
    {
        for(auto x:rasp[i])
            g << x<< " ";
        g << '\n';
    }

}