#include <fstream>
#include <vector>
#include <stack>

#define pb push_back
#define nMax 100005
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int viz[nMax], Lev[nMax], Low[nMax], n, m, index, nrctc;
stack<int> Stck;
vector<int> CTC[nMax];
vector<int> G[nMax];
void read()
{
    int a, b;
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        fin>>a>>b;
        G[a].pb(b);
    }
}
void Tarjan(int node)
{
    int son, papa;
    viz[node]=1;
    Stck.push(node);
    Lev[node]=Low[node]=++index;
    for(vector<int>::iterator it=G[node].begin();it!=G[node].end();it++)
    {
        son=*it;
        if(Lev[son]==0)
        {
            Tarjan(son);
            Low[node]=min(Low[node], Low[son]);
        }
        else
            if(viz[son]==1)
                Low[node]=min(Low[node], Low[son]);
    }
    if(Lev[node]==Low[node])
    {
        nrctc++;
        do
        {
            papa=Stck.top();
            Stck.pop();
            viz[papa]=0;
            CTC[nrctc].pb(papa);
        }
        while(papa!=node);
    }
}
void solve()
{
    for(int i=1;i<=n;i++)
        if(Lev[i]==0)
            Tarjan(i);
}
void write()
{
    fout<<nrctc<<'\n';
    for(int i=1;i<=n;i++)
    {
        for(vector<int>::iterator it=CTC[i].begin();it!=CTC[i].end();it++)
            fout<<*it<<" ";
        fout<<'\n';
    }

}
int main()
{
    read();
    solve();
    write();
    return 0;
}