#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#define Nmax 100005
using namespace std;
ifstream fin ("ctc.in");
ofstream fout ("ctc.out");
vector <int> G[Nmax];
vector <int> T[Nmax],sol[Nmax];
int n,m,nrsol;
int v[Nmax];
stack <int> s;
void DFS1 (int nod)
{
    int i,vec;
    v[nod]=1;
    for (i=0;i<G[nod].size();i++)
    {
        vec=G[nod][i];
        if (v[vec]==0)
            DFS1(vec);
    }
    s.push(nod);
}
void DFS2(int nod)
{
    int i,vec;
    sol[nrsol].push_back(nod);
    v[nod]=1;
    for (i=0;i<T[nod].size();i++)
    {
        vec=T[nod][i];
        if (v[vec]==0)
            DFS2(vec);
    }
}
int main()
{
    int i,j,x,y;
    fin>>n>>m;
    for (i=1;i<=m;i++)
    {
        fin>>x>>y;
        G[x].push_back(y);
        T[y].push_back(x);
    }
    for (i=1;i<=n;i++)
    {
        if (v[i]==0)
            DFS1(i);
    }
    for (i=1;i<=n;i++)
        v[i]=0;
    while (!s.empty())
    {
        x=s.top();
        if (v[x]==0)
        {
            nrsol++;
            DFS2(x);
        }
        s.pop();
    }
    fout<<nrsol<<"\n";
    for (i=1;i<=nrsol;i++)
    {
        for (j=0;j<sol[i].size();j++)
            fout<<sol[i][j]<<" ";
        fout<<"\n";
    }
    fin.close();
    fout.close();
    return 0;
}