#include <fstream>
#include <vector>
#define nMax 100005
#define pb push_back
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int viz[nMax], Lev[nMax], Low[nMax], index, nrctc, n, m;
vector<int> G[nMax], CTC[nMax], stck;
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 curr;
    viz[node]=1;
    Lev[node]=Low[node]=++index;
    stck.pb(node);
    for(vector<int>::iterator it=G[node].begin();it!=G[node].end();it++)
    {
        int fiu=*it;
        if(Lev[fiu]==0)
        {
            tarjan(fiu);
            Low[node]=min(Low[node], Low[fiu]);
        }
        else
            if(viz[fiu]==1)
                Low[node]=min(Low[node], Low[fiu]);
    }
    if(Lev[node]==Low[node])
    {
        nrctc++;
        do
        {
            curr=stck.back();
            stck.pop_back();
            CTC[nrctc].pb(curr);
            viz[curr]=0;
        }
        while(curr!=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<=nrctc;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;
}