#include <iostream>
#include <fstream>
#include <vector>
#include <cstring>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
#define MAX 100010
#define cout fout
typedef vector<int> :: iterator iter;
vector <int> G[MAX], Gt[MAX], ans;
vector < vector <int> > rez;

int viz[MAX], n, m, st[MAX], dr, x, y;

void df(int nod)
{
    if(viz[nod])
        return;
    viz[nod] = 1;
    for(iter it = G[nod].begin() ; it != G[nod].end() ; it++)
    {
        df(*it);
    }
    st[++dr] = nod;
}

void df2(int nod)
{
    if(viz[nod])
        return;
    viz[nod] = 1;
    ans.push_back(nod);
    for(iter it = Gt[nod].begin() ; it != Gt[nod].end() ; it++)
    {
        df2(*it);
    }
}

int main()
{
    int i;
    fin >> n >> m;
    while(m--)
    {
        fin >> x >> y;
        G[x].push_back(y);
        Gt[y].push_back(x);
    }
    for(i = 1 ; i <= n ; i++)
        df(i);
    memset(viz, 0, sizeof(viz));
    for(i = n ; i >= 1 ; i--)
    {
        if(!viz[st[i]])
        {
            df2(st[i]);
            rez.push_back(ans);
            ans.clear();
        }
    }
    cout << rez.size() << "\n";
    for(vector<vector<int> > :: iterator it = rez.begin() ; it != rez.end() ; it ++)
    {
        for(iter it1 = it->begin() ; it1 != it->end() ; it1++)
        {
            cout << *it1 << " ";
        }
        cout << "\n";
    }
}