#include <fstream>
#include <vector>
using namespace std;
ifstream in ("ctc.in");
ofstream out ("ctc.out");

const int NMax=100005;
int n, m, use[NMax], nrctc, nr, x[NMax];
vector <int> G[NMax], sol[NMax], GT[NMax];

void Read()
{
    in>>n>>m;
    while(m--)
    {
        int x,y;
        in>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}
void dfs_secund(int nodarg)
{
    sol[nrctc].push_back(nodarg);
    use[nodarg]=0;
    for (int i=0;i<(int)GT[nodarg].size();i++)
    {
        int vecin=GT[nodarg][i];
        if(use[vecin]==1)
        {
            dfs_secund(vecin);
        }
    }
}
void dfs_prim(int nodarg)
{
    use[nodarg]=1;
    for(int i=0;i<(int)G[nodarg].size();i++)
    {
        int vecin=G[nodarg][i];
        if(use[vecin]==0)
        {
            dfs_prim(vecin);
        }
    }
    x[++nr]=nodarg;
}
void Solve()
{
    for (int i=1;i<=n;i++)
    {
        if(!use[i])
            dfs_prim(i);
    }
    for (int i=n;i>=1;i--)
    {
        if(use[x[i]]==1)
        {
            nrctc++;
            dfs_secund(x[i]);
        }
    }
}
void Print()
{
    out<<nrctc<<'\n';
    for(int i=1;i<=nrctc;i++)
    {
        for(int j=0;j<(int)sol[i].size();j++)
        {
            out<<sol[i][j]<<' ';
        }
        out<<'\n';
    }
}
int main()
{
    Read();
    Solve();
    Print();
}