# include <fstream>
# include <vector>
# define DIM 100001
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
int n,m,i,d,k,v[DIM];
vector<int> a[DIM],b[DIM],s[DIM];
bool p[DIM];
void read()
{
    int x,y;
    f>>n>>m;
    for(i=1;i<=m;i++)
         {
          f>>x>>y;
          a[x].push_back(y);
          b[y].push_back(x);
         }
}
void DFS(int x)
{
    int i,n=a[x].size();
    p[x]=1;
    for(i=0;i<n;i++)
        if(!p[a[x][i]])
            DFS(a[x][i]);
    v[++d]=x;
}
void DFS2(int x)
{
    int i,n=b[x].size();
    p[x]=0;
    s[k].push_back(x);
    for(i=0;i<n;i++)
        if(p[b[x][i]])
            DFS2(b[x][i]);
}
void Kosaraju()
{
    for(i=1;i<=n;i++)
         if(!p[i])
             DFS(i);
    for(i=n;i;i--)
         if(p[v[i]])
            {
             k++;
             DFS2(v[i]);
            }
}
void write()
{
    int j;
    g<<k<<'\n';
    for(i=1;i<=k;i++)
        {
         d=s[i].size();
         for(j=0;j<d;j++)
              g<<s[i][j]<<" ";
         g<<'\n';
        }
}
int main()
{
    read();
    Kosaraju();
    write();
    f.close();
    g.close();
    return 0;
}