#include <bits/stdc++.h>
using namespace std;
const int nmax=1e5+5;
ifstream f("ctc.in");
ofstream g("ctc.out");
vector<int>adj[nmax];
vector<int> adjt[nmax];
stack <int> s;
bool v[nmax];
vector <int> ans[nmax];
void dfs1 (int x)
{
    v[x]=1;
    for(auto it: adj[x])
    {
            if(!v[it])
                {dfs1(it);
               
                }
    }
    s.push(x);
}
void dfs2(int x,int k)
{
    v[x]=1;
    ans[k].push_back(x);
    for(auto it : adjt[x])
        if(!v[it])
            dfs2(it,k);

}

int main ()

{
    int n,m;
    f>>n>>m;
    while(m--)
    {   int x,y;
        f>>x>>y;
        adj[x].push_back(y);
        adjt[y].push_back(x);


    }
    for(int i=1;i<=n;i++)
             dfs1(i);
    for(int  i=1;i<=n;i++)
        v[i]=0;
    int k=1;
    while(!s.empty())
    {
        int nod =s.top();
        s.pop();
        if(!v[nod])
        {
            dfs2(nod,k);
            k++;

        }
    }
    g<<k-1;
    for(int i=1;i<k;i++)
    {
        g<<'\n';
        for(auto it : ans[i])
            g<<it<<' ';
    }




}