#include <fstream>
#include <stack>
#include <vector>

using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");
int n,m,k,nod;
stack<int> s;
vector<int> index, lowl;
vector<bool> inStiva;
vector<vector<int>> adiac;
vector<vector<int>> ctc;

void tarjan(int v)
{
    s.push(v);
    inStiva[v] = true;
    index[v] = k;
    lowl[v] = k;
    k++;

    for(auto vec : adiac[v])
        {
        if (index[vec] == -1)
            tarjan(vec);
        if (inStiva[vec] == true)
            lowl[v] = min(lowl[v],lowl[vec]);
        }

    if(lowl[v] == index[v])
        {
         vector<int>comp;
         do
            {
            nod = s.top();
            lowl[nod] = index[v];
            comp.push_back(nod);
            inStiva[nod] = false;
            s.pop();
            }while(nod != v);
         ctc.push_back(comp);
        }

}

void afis()
{
    g<<ctc.size()<<"\n";
    int k=0,ok;

    for(auto comp: ctc)
    {
        for(auto v: comp)
            g << v <<" ";
        g << "\n";
    }
}

int main()
{
    int a, b;
    f >> n >> m;

    index.resize(n+1); index.assign(n+1,-1);
    lowl.resize(n+1); lowl.assign(n+1,-1);
    inStiva.resize(n+1); inStiva.assign(n+1,false);
    adiac.resize(n+1);

    for (int i = 0; i < m; i++)
        {
         f >> a >> b;
         adiac[a].push_back(b);
        }

    for (int i = 1; i <= n; i++)
        {
         if(index[i] == -1)
            tarjan(i);
        }

    afis();

    return 0;
}