#include <iostream>
#include <fstream>
#include <vector>
#define NMAX 100001
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");

vector <int> G[NMAX],Gt[NMAX],St[NMAX];
vector<int>S;
int viz[100001];
 int k=0;

void dfs(int nod)
{
    viz[nod]=1;
    for(unsigned int i=0;i<G[nod].size();i++)
        if(viz[G[nod][i]]==0)
            dfs(G[nod][i]);
    S.push_back(nod);
}

void dfs1(int nod)
{
    St[k].push_back(nod);
    viz[nod]=1;
    for(unsigned int i=0;i<Gt[nod].size();i++)
        if(viz[Gt[nod][i]]==0)
            dfs1(Gt[nod][i]);
}

int main()
{
    int n,m,i,x,y;
    f>>n>>m;
    for(i=1;i<=m;i++)
    {
        f>>x>>y;
        G[x].push_back(y);
        Gt[y].push_back(x);
    }
    for(i=1;i<=n;i++)
        if(viz[i]==0)
            dfs(i);
    for(i=1;i<=n;i++)
        viz[i]=0;
    for(i=n-1;i>=0;i--)
        if(viz[S[i]]==0)
        {
            k++;
            dfs1(S[i]);
        }
    g<<k<<"\n";
    for(i=1;i<=k;i++)
    {
        for(unsigned int j=0;j<St[i].size();j++)
            g<<St[i][j]<<" ";
        g<<"\n";
    }
    return 0;
}