#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
int n,i,m,x,y,viz[100001],ver[100001],q[100001],nr;
vector <int> v[100001],L[100001],r[100001];
ifstream f("ctc.in");
ofstream g("ctc.out");
void DF(int x)
{
    viz[x]=1;
    for(auto it=v[x].begin();it!=v[x].end();it++)
        if(viz[*it]==0)
        DF(*it);
    q[++nr]=x;
}
void DF1(int x)
{
    ver[x]=1;r[nr].push_back(x);
    for(auto it=L[x].begin();it!=L[x].end();it++)
      if(ver[*it]==0)
        DF1(*it);
}
int main()
{
    f>>n>>m;
    for(i=1;i<=m;i++)
    {
        f>>x>>y;
        v[x].push_back(y);
        L[y].push_back(x);
    }
    DF(1);
    nr=0;
    for(i=n;i>=1;i--)
        if(ver[q[i]]==0)
    {
        nr++;
        DF1(q[i]);

    }
    g<<nr<<endl;
    for(i=1;i<=nr;i++)
    {
        for(auto it=r[i].begin();it!=r[i].end();it++)
            g<<*it<<" ";
        g<<endl;
    }
    return 0;
}