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

    return 0;
}