#include <iostream>
#include <fstream>
#include <vector>
#define NMAX 100005
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
int n,m,x,y,i,start[NMAX],cnt,componente;
vector <int> v[NMAX],vt[NMAX],ans[NMAX];
bool visited[NMAX];
void DFS(int node)
{
    visited[node]=1;
    for(auto & it : v[node])
    {
        if(!visited[it])
        {
            DFS(it);
        }
    }
    start[++cnt]=node;
}
void DFS2(int node)
{
    visited[node]=0;
    ans[componente].push_back(node);
    for(auto & it : v[node])
    {
        if(visited[it])
        {
            DFS2(it);
        }
    }
}
int main()
{
    f>>n>>m;
    for(i=1;i<=m;i++)
    {
        f>>x>>y;
        v[x].push_back(y);
        vt[y].push_back(x);
    }
    for(i=1;i<=n;i++)
    {
        if(!visited[i])
        {
            DFS(i);
        }
    }
    for(i=1;i<=n;i++)
    {
        if(visited[start[i]])
        {
            ++componente;
            DFS2(start[i]);
        }
    }
    g<<componente<<"\n";
    for(i=1;i<=componente;i++)
    {
        for(auto & it : ans[i])
        {
            g<<it<<" ";
        }
        g<<"\n";
    }
    return 0;
}