#include <bits/stdc++.h>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
const int nmax=100001;
int n,m,timp[nmax],k,nrsol;
vector<int>G[nmax];
vector<int>H[nmax];
vector<int>sol[nmax];
///Complexitate O(n+m)
bitset<nmax>viz;
void DFS1(int varf)
{
    viz[varf]=1;
    for(int i=0;i<G[varf].size();i++)
            if(!viz[G[varf][i]])
                    DFS1(G[varf][i]);
    ++k;
    timp[k]=varf;
}
void DFS2(int varf)
{
    viz[varf]=1;
    for(int i=0;i<H[varf].size();i++)
            if(!viz[H[varf][i]])
                DFS2(H[varf][i]);
    sol[nrsol].push_back(varf);
}
int main()
{
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        int x,y;
        fin>>x>>y;
        G[x].push_back(y);
        H[y].push_back(x);
    }
    for(int i=1;i<=n;i++)
        if(!viz[i])
            DFS1(i);
    viz.reset();
    for(int i=k;i>=1;i--)
        if(!viz[timp[i]])
    {
        nrsol++;
        DFS2(timp[i]);
    }
    fout<<nrsol<<"\n";
    for(int i=1;i<=nrsol;i++)
    {
        sort(sol[i].begin(),sol[i].end());
        for(int j=0;j<sol[i].size();j++)
                fout<<sol[i][j]<<" ";
        fout<<"\n";
    }
    fin.close();
    fout.close();
    return 0;
}