#include <fstream>
#include <vector>
using namespace std;
ifstream cin("ctc.in");
ofstream cout("ctc.out");
using pii = pair<int,int>;
const int nmax = 1e5 + 1;
vector <int> g[nmax];
vector <int> t[nmax];
int n , m , a , b, ind , top[nmax];
bool viz[nmax];
vector <int> aux;
void tsort(int x)
{
    viz[x] = 1;
    for(auto it : g[x])
    {
        if(!viz[it]) tsort(it);
    }
    top[ind--] = x;
}
vector <vector <int>> ctc;
void find_ctc(int x)
{
    viz[x] = 1;
    aux.push_back(x);
    for(auto it : t[x])
    {
        if(!viz[it]) find_ctc(it);
    }
}
signed main()
{
    cin >> n >> m;
    ind = n;
    for(int i = 1 ; i <= m ; ++i)
    {
        cin >> a >> b;
        g[a].push_back(b);
        t[b].push_back(a);
    }
    for(int i = 1 ; i <= n ; ++i) if(!viz[i]) tsort(i);
    for(int i = 1 ; i <= n ; ++i) viz[i] = 0;
    for(int i = 1 ; i <= n ; ++i)
    {
        if(!viz[top[i]])
        {
            aux.clear();
            find_ctc(top[i]);
            ctc.push_back(aux);
        }
    }
    cout << ctc.size() << '\n';
    for(auto ala : ctc)
    {
        for(auto it : ala)
        {
            cout << it <<' ';
        }
        cout << '\n';
    }
    return 0;
}