#include<fstream>
#include<vector>
#include<queue>
using namespace std;
ifstream fin ("ctc.in");
ofstream fout("ctc.out");
int i,n,m,k,nrcon,x,y,topo[100010],viz[100010];
vector < int > v[100010],v2[100010];
queue < int > q[100010];
void dfs1(int nod)
{
    viz[nod]=1;
    for(auto it : v[nod])
        if(viz[it]==0)
            dfs1(it);
    topo[k--]=nod;
}
void dfs2(int nod)
{
    viz[nod]=1;
    q[nrcon].push(nod);
    for(auto it: v2[nod])
        if(viz[it]==0)
            dfs2(it);
}
int main()
{
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>x>>y;
        v[x].push_back(y);
        v2[y].push_back(x);
    }
    k=n;
    for(i=1;i<=n;i++)
        if(viz[i]==0)
            dfs1(i);
    for(i=1;i<=n;i++)
        viz[i]=0;
    for(i=1;i<=n;i++)
        if(viz[topo[i]]==0)
        {
            nrcon++;
            dfs2(topo[i]);
        }
    fout<<nrcon<<'\n';
    for(i=1;i<=nrcon;i++)
    {
        while(!q[i].empty())
        {
            fout<<q[i].front()<<' ';
            q[i].pop();
        }
        fout<<'\n';
    }
    fin.close();
    fout.close();
    return 0;
}