# include <fstream>
# include <vector>
# include <algorithm>
# define NMax 100005
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
vector <int> v[NMax];
vector <int> t[NMax];
vector <int> sol[NMax];
int ant[NMax],ap[NMax];
int i,j,n,m,SOL,x,y,nr;
void dfs (int k)
{
    int i;
    ap[k]=1;
    for (i=0; i<v[k].size(); ++i)
        if (!ap[v[k][i]]) dfs(v[k][i]);
    ant[++nr]=k;
}
void dfst (int k)
{
    int i;
    ap[k]=0;
    sol[SOL].push_back(k);
    for (i=0; i<t[k].size(); ++i)
        if (ap[t[k][i]]) dfst(t[k][i]);
}
int main ()
{
    f>>n>>m;
    for (i=1; i<=m; ++i)
    {
        f>>x>>y;
        v[x].push_back(y);
        t[y].push_back(x);
    }
    for (i=1; i<=n; ++i)
        if (! ap[i]) dfs (i);
    for (i=n; i>=1; --i)
    {
        if (ap[ant[i]])
        {
            ++SOL;
            dfst (ant[i]);
        }
    }
    g<<SOL<<"\n";
    for (i=1; i<=SOL; ++i)
    {
        for (j=0; j<sol[i].size(); ++j)
            g<<sol[i][j]<<" ";
        g<<"\n";
    }

    return 0;
}