#include <fstream>
#include <cstring>
#include <vector>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int n,m,s[200001],k,viz[100001],comp;
vector <int> G[100001],GT[100001];
void dfs(int nod)
{
    viz[nod]=1;

    for(auto i:G[nod])
    {
        if(viz[i]==0)
        {
            dfs(i);
        }
    }
    k++;
    s[k]=nod;
}
void dfst(int nod,int x)
{
    viz[nod]=1;
    if(x==1)
    fout<<nod<<" ";
    for(auto i:GT[nod])
    {
        if(viz[i]==0)
        {
            dfst(i,x);
        }
    }

}
int main()
{
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        int x,y;
        fin>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    for(int i=1;i<=n;i++)
    {
        if(viz[i]==0)
        {
            dfs(i);
        }
    }
        memset(viz,0,sizeof(viz));

    for(int i=k;i>=1;i--)
    {
        if(viz[s[i]]==0)
        {


            comp++;
            dfst(s[i],0);
        }
    }
    fout<<comp<<"\n";
    memset(viz,0,sizeof(viz));

    for(int i=k;i>=1;i--)
    {
        if(viz[s[i]]==0)
        {
            dfst(s[i],1);
            fout<<"\n";
        }
    }

    return 0;
}