#include<fstream>
#include<vector>
#include<stack>
#define pb push_back
using namespace std;

ifstream cin("ctc.in");
ofstream cout("ctc.out");

const int NMAX = 1e5 + 1;

vector<int> vecini[NMAX];
vector<int> ant[NMAX];
vector<bool> viz(NMAX),kosa(NMAX);
vector<int> compo[NMAX];

stack<int> stiva;

void dfs(int nod)
{
    viz[nod] = 1;
    for(auto v : vecini[nod])
        {
            if(!viz[v])
                dfs(v);
        }

    stiva.push(nod);
}

void k(int nod,int nr)
{
    kosa[nod] = 1;
    for(auto it : ant[nod])
        {
            if(!kosa[it])
                k(it,nr);
        }

    compo[nr].pb(nod);
}

int main()
{
    int n,m,a,b,comp = 0;
    cin >> n >> m;

    for(int i = 0 ; i < m ; i++)
        {
            cin >> a >> b;
            vecini[a].pb(b);
            ant[b].pb(a);
        }

    for(int i = 1; i <= n ; i++)
        {
            if(!viz[i])
                dfs(i);
        }

    // kosaraju
    while(!stiva.empty())
        {
            int nod = stiva.top();
            stiva.pop();

            if(!kosa[nod])
                {
                    k(nod,++comp);
                }
        }

    cout << comp << '\n';
    for(int i = 1; i <= comp ; i++)
        {
            for(auto it : compo[i])
                {
                    cout << it << " ";
                }

            cout << '\n';
        }
}