#include <iostream>
#include <fstream>
#include <vector>
#include <cstring>
using namespace std;

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

int n,m;
const int maxn=100010;
vector <int> Graf[maxn],Graft[maxn],Comp;
vector < vector <int> > Sol;
int Sort[maxn];

bool ok,viz[maxn];

void SortTop(int nod)
{
    viz[nod]=1;
    vector <int> :: iterator it;
    for(it=Graft[nod].begin();it!=Graft[nod].end();it++)
        if(!viz[*it])
            SortTop(*it);
    Sort[++Sort[0]]=nod;

}

void DFS(int nod)
{
    viz[nod]=1;
    Comp.push_back(nod);
    vector <int> :: iterator it;
    for(it=Graf[nod].begin();it!=Graf[nod].end();it++)
        if(!viz[*it])
            DFS(*it);

}


int main()
{
    int i,x,y;
    in>>n>>m;
    for(i=1;i<=m;i++)
    {
        in>>x>>y;
        Graf[x].push_back(y);
        Graft[y].push_back(x);
    }
    for(i=1;i<=n;i++)
        if(!viz[i])
            SortTop(i);

    memset(viz,0,sizeof(viz));


    for(i=n;i>=0;i--)
        if(!viz[Sort[i]])
        {
            DFS(Sort[i]);
            Sol.push_back(Comp);
            Comp.clear();
        }

    out<<Sol.size()<<"\n";
    for(i=0;i<Sol.size();i++,out<<"\n")
        for(vector  <int>  :: iterator it = Sol[i].begin();it!=Sol[i].end();it++)
            out<<*it<<" ";
    return 0;
}