#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
ifstream f ("ctc.in");
ofstream g ("ctc.out");
int n,m,cnt,comp;
bool viz[100001];
int ordine_DFS[100001];
vector<int>adiacenta[1000001];
vector<int>adiacenta_compl[1000001];
void citire()
{
    f >> n >> m;
    for(int i =1; i<=m; i++)
    {
        int x,y;
        f >> x >> y;
        adiacenta[x].push_back(y);
        adiacenta_compl[y].push_back(x);
    }
}
void DFS(int nod)
{
    viz[nod] = 1;
    for(auto x:adiacenta[nod])
    {
        if(!viz[x])
            DFS(x);
    }
    ordine_DFS[++cnt] = nod;
}
void DFS_compl(int nod)
{
    viz[nod] = 1;
    for(auto x:adiacenta_compl[nod])
    {
        if(!viz[x])
            DFS_compl(x);
    }
    ordine_DFS[++cnt] = nod;
}
void resetare()
{
    for(int i = 0; i<=100000; i++)
        viz[i] = 0;
}
void gasire_comp()
{
    for(int i= n; i>=1; i--)
    {
        int nod = ordine_DFS[i];
        if(!viz[nod])
        {
            comp++;
            DFS_compl(nod);
        }
    }
    g << comp<< endl;
    resetare();
    for(int i= n; i>=1; i--)
    {
        int nod = ordine_DFS[i];
        if(!viz[nod])
        {
            cnt = 0;
            DFS_compl(nod);
            for(int j = 1;j<=cnt;j++)
                g << ordine_DFS[j]<< " ";
            g << endl;
        }
    }
}
int main()
{
    citire();
    for(int i = 1; i<=n; i++)
    {
        if(!viz[i])

            DFS(i);
    }
    resetare();
    gasire_comp();

}