#include <iostream>
#include <vector>
#include <fstream>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
vector <int> v[100001];
vector <int> v1[100001];
vector <int> v2[100001];
int n,m,t[100001],k;
bool viz[100001],viz1[100001];
void dfs(int x)
{
    vector <int>::iterator it;
    viz[x]=1;
    for(it=v[x].begin();it!=v[x].end();++it)
        if(!viz[*it])
            dfs(*it);
    t[++k]=x;
}
void dfs1(int x,int nr)
{
    vector <int>::iterator it;
    viz1[x]=1;
    for(it=v[x].begin();it!=v[x].end();++it)
        if(!viz1[*it])
            dfs1(*it,nr);
    v2[nr].push_back(x);
}
int main()
{
    int i,x,y,j,nr=0;
    vector <int>::iterator it;
fin>>n>>m;
for(i=1;i<=m;i++)
{
    fin>>x>>y;
    v[x].push_back(y);
    v1[y].push_back(x);
}
fin.close();
for(i=1;i<=n;i++)
    if(viz[i]==0)
        dfs(i);
for(i=k;i>=1;i--)
    if(viz1[i]==0)
    {   nr++;
        dfs1(i,nr);
    }
fout<<nr<<"\n";
for(i=1;i<=nr;i++)
{
    for(it=v2[i].begin();it!=v2[i].end();++it)
        fout<<*it<<" ";
    fout<<"\n";
}
    return 0;
}