#include<fstream>
#include<vector>
using namespace std;
int index[100001],low[100001],s[100001],m,n,nr=1,u,k,viz[100001];
vector<int>v[100001],sol[100001];
ifstream fin("ctc.in");
ofstream fout("ctc.out");
void citire()
{
    int x,y;
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        fin>>x>>y;
        v[x].push_back(y);
    }
}

void tarjan(int nod)
{
    index[nod]=low[nod]=nr;
    nr++;
    s[++u]=nod;
    viz[nod]=1;
    for(int i=0;i<v[nod].size();i++)
    {

        if(index[v[nod][i]]==0)
        {
            tarjan(v[nod][i]);
            if(low[nod]>low[v[nod][i]])
            {
                low[nod]=low[v[nod][i]];
            }
        }
        else
        if(viz[v[nod][i]]==1)
        {
            if(low[nod]>index[v[nod][i]])
            {
                low[nod]=index[v[nod][i]];
            }

        }
    }
    if(low[nod]==index[nod])
    {
                k++;
                while(u>0 && s[u]!=nod)
                {
                    sol[k].push_back(s[u]);
                    viz[s[u]]=0;
                    u--;
                }
                sol[k].push_back(nod);
                viz[nod]=0;
                u--;
    }

}

void afisare()
{
    fout<<k<<"\n";
    for(int i=1;i<=k;i++)
    {
        for(int j=0;j<sol[i].size();j++)
        {
            fout<<sol[i][j]<<" ";
        }
        fout<<"\n";
    }
}

int main()
{
    citire();
    for(int i=1;i<=n;i++)
    {
        if(index[i]==0)
        {
            tarjan(i);
        }
    }
    afisare();
    return 0;
}