#include <fstream>
#include <vector>
#define NMAX 100003
using namespace std;

ifstream fin ("ctc.in");
ofstream fout ("ctc.out");

int n,m,k,niv,cnt;
int stiv[NMAX];
int nivel[NMAX],lw[NMAX];
bool viz[NMAX];
vector<int> compConex[NMAX];
vector<int>graf[NMAX];

void dfs(int nod)
{
    viz[nod]=true;
    stiv[++k]=nod;
    nivel[nod]=++niv;
    lw[nod]=niv;
    for(int i=0; i<graf[nod].size(); i++)
    {
        int nd=graf[nod][i];
        if(nivel[nd]==0)
        {
            dfs(nd);
            lw[nod]=min(lw[nod],lw[nd]);

        }
        else if(viz[nd]){
            lw[nod]=min(lw[nod],nivel[nd]);//muchie de intoarcere
        }

    }
    if(lw[nod]==nivel[nod])
    {
        //e cmp conexa
        cnt++;
        do{
            compConex[cnt].push_back(stiv[k]);
            viz[stiv[k]]=false;
            k--;
        }while(k>0 && stiv[k+1]!=nod);

    }
    //fout<<nod;
}



int main()
{
    fin>>n>>m;
    for(int i=1; i<=m; i++)
    {
        int x,y;
        fin>>x>>y;
        graf[x].push_back(y);

    }
    for(int i=1; i<=n; i++)
    {
        if(nivel[i]==0)
        {
            dfs(i);
        }
    }
    fout<<cnt<<"\n";
    for(int i=1; i<=cnt; i++)
    {
        for(int j=0; j<compConex[i].size(); j++)
        {
            fout<<compConex[i][j]<<" ";
        }
        fout<<"\n";
    }
    return 0;
}