#include <fstream>
#include <algorithm>
#include <vector>
using namespace std;
ifstream cin ("ctc.in");
ofstream cout ("ctc.out");
int n,i,j,vf,x,y,m;
int viz[100005],v[100005],cnt;
vector <int> G1[100005];
vector <int> G2[100005];
vector <int> rasp[100005];
void postordine(int nod)
{
    viz[nod]=1;
    vector<int>::iterator i;
    for(i=G1[nod].begin();i!=G1[nod].end();i++)
    {
        if(viz[*i]==0)
        postordine(*i);
    }
    v[++vf]=nod;
}
void dfs(int nod)
{
    viz[nod]=1;
    rasp[cnt].push_back(nod);
    vector<int>::iterator i;
    for(i=G2[nod].begin();i!=G2[nod].end();i++)
    {
        if(viz[*i]==0)
        dfs(*i);
    }
}
int main()
{
    cin>>n>>m;
    for(i=1;i<=m;i++)
    {
        cin>>x>>y;
        G1[x].push_back(y);
        G2[y].push_back(x);
    }
    for(i=1;i<=n;i++)
        if(viz[i]==0)
            postordine(i);
    for(i=1;i<=n;i++)
        viz[i]=0;
    for(i=vf;i>=1;i--)
    {
        if(viz[v[i]]==0)
        {
            cnt++;
            dfs(v[i]);
        }
    }
    cout<<cnt<<'\n';
    for(i=1;i<=cnt;i++)
    {
        for(j=0;j<=rasp[i].size()-1;j++)
            cout<<rasp[i][j]<<' ';
        cout<<'\n';
    }
    return 0;
}