#include <iostream>
#include <fstream>
#include <stack>
#include <vector>
#define Nmax 100005
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
stack<int>st;
int low[Nmax],h[Nmax],pas,inq[Nmax],a,b,viz[Nmax],N,M,k;
vector<int>gr[Nmax],v[Nmax];
void ctc(int nod)
{
    low[nod]=h[nod]=pas;
    viz[nod]=1;
    pas++;
    st.push(nod);
    inq[nod]=1;
    for(int i=0;i<gr[nod].size();i++)
    {
        if(!viz[gr[nod][i]])
        {
            ctc(gr[nod][i]);
            low[nod]=min(low[nod],low[gr[nod][i]]);
        }
        else if(inq[nod]==1)
            low[nod]=min(low[nod],h[gr[nod][i]]);
    }
    if(low[nod]==h[nod])
    {
        ++k;
        while(st.top()!=nod)
        {
            v[k].push_back(st.top());
            inq[st.top()]=0;
            st.pop();
        }
        inq[st.top()]=0;
        v[k].push_back(st.top());
        st.pop();
    }
}
int main()
{
    fin>>N>>M;
    for(int i=1;i<=M;i++)
    {
        fin>>a>>b;
        gr[a].push_back(b);
    }
    for(int i=1;i<=N;i++)
    if(!viz[i])
    {
        pas=1;
        ctc(i);
    }
    fout<<k<<'\n';
    for(int i=1;i<=k;i++,fout<<'\n')
        for(int j=0;j<v[i].size();j++)
            fout<<v[i][j]<<" ";
    return 0;
}