#include <fstream>
#include <vector>
#include <stack>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
const int nmax=100005;
int n, m, viz[nmax], viz2[nmax], nr, cc[nmax];
stack <int> st;
vector <int> muchii[nmax]; //graf initial
vector <int> muchii2[nmax]; //graf transpus
void dfs(int nod)
{
    viz[nod]=1;
    for (int i=0; i<muchii[nod].size(); i++)
    {
        int vecin=muchii[nod][i];
        if (!viz[vecin])
            dfs(vecin);
    }
    st.push(nod); //la finalizarea nodului, il adaugam in stiva
}
void dfs2(int nod)
{
    viz2[nod]=1;
    cc[nod]=nr;
    for (int i=0; i<muchii2[nod].size(); i++)
    {
        int vecin=muchii2[nod][i];
        if(!viz2[vecin])
            dfs2(vecin);
    }
}
int main()
{
    fin >> n >> m;
    for (int i=1; i<=m; i++)
    {
        int x, y;
        fin >> x >> y;
        muchii[x].push_back(y);
        muchii2[y].push_back(x);
    }
    dfs(1);
    while(!st.empty())
    {
        int nod=st.top();
        st.pop();
        if(!viz2[nod])
        {
            nr++;
            dfs2(nod);
        }
    }
    fout << nr << '\n';
    for (int i=1; i<=nr; i++)
    {
        for (int j=1; j<=n; j++)
            if (cc[j]==i)
                fout << j << " ";
        fout << '\n';
    }
    return 0;
}