#include <fstream>
#include <stack>
#include <vector>
#include <algorithm>
using namespace std;
ifstream cin("ctc.in");
ofstream cout("ctc.out");
vector<int> graf[100005],graf2[100005],rasp[100001];
stack<int> st;
int n,m,i,j,x,y,crt,nr_ctc;
bool viz[100005];
void dfs_1(int nod)
{
    for(int i=0; i<graf[nod].size(); i++)
        if(!viz[graf[nod][i]])
        {
            viz[graf[nod][i]]=true;
            dfs_1(graf[nod][i]);
        }
    st.push(nod);

}
void dfs_2(int nod)
{
    for(int i=0; i<graf2[nod].size(); i++)
    {
        if(!viz[graf2[nod][i]])
        {
            viz[graf2[nod][i]]=true;
            dfs_2(graf2[nod][i]);
        }
    }
    rasp[nr_ctc].push_back(nod);

}
int main()
{
    cin>>n>>m;
    for(i=1; i<=m; i++)
    {
        cin>>x>>y;
        graf[x].push_back(y);
        graf2[y].push_back(x);
    }
    for(i=1; i<=n; i++)
        if(!viz[i])
        {
            viz[i]=1;
            dfs_1(i);
        }

    for(i=1; i<=n; i++)
        viz[i]=false;

    while(!st.empty())
    {
        crt=st.top(); st.pop();
        if(viz[crt])
            continue;

        nr_ctc++; viz[crt]=true;
        dfs_2(crt);
    }
    cout<<nr_ctc<<"\n";
    for(i=1; i<=nr_ctc; i++)
    {
        sort(rasp[i].begin(),rasp[i].end());
        for(j=0; j<rasp[i].size(); j++)
            cout<<rasp[i][j]<<" ";
        cout<<"\n";
    }

}