#include <iostream>
#include <fstream>
#include <vector>
#define Nmax 100010
#include <stack>
using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");

int n,m,vis[Nmax],vis2[Nmax],nr;
vector<int> graf[Nmax],Tgraf[Nmax],sol[Nmax];
stack<int> s;

void dfs1(int v)
{
    vis[v]=1;
    for(int i=0;i<graf[v].size();i++)
        if(vis[graf[v][i]]==0)
        {
            dfs1(graf[v][i]);
        }
    s.push(v);
}
void dfs2(int v)
{
    sol[nr].push_back(v);
    vis2[v]=1;
    for(int i=0;i<Tgraf[v].size();i++)
    {
        int w=Tgraf[v][i];
        if(vis2[w]==0)
        {
            dfs2(w);
        }
    }

}
int main()
{
    f >> n >> m;
    int x,y;
    for(int i=0;i<m;i++)
    {
        f >> x >> y;
        graf[x].push_back(y);
        Tgraf[y].push_back(x);

    }
    for(int i=1;i<=n;i++)
        if(vis[i]==0)
            dfs1(i);

    while(!s.empty())
    {
        int v=s.top();
        s.pop();
        if(vis2[v]==0)
        {
            nr++;
            dfs2(v);
        }
    }

    g << nr << "\n";
    for(int i=1;i<=nr;i++){
        for(int j=0;j<sol[i].size();j++)
            g << sol[i][j] << " ";
        g << "\n";
    }

    return 0;
}