#include <bits/stdc++.h>
#define NMAX 100005
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
vector <int> v[NMAX], vt[NMAX], Sol[NMAX];
bool viz[NMAX];
int postordine[NMAX];
int k,N,M;
int cul[NMAX], culoare;
void dfs1(int x)
{
    viz[x]=1;
    for(vector<int>::iterator vecin=v[x].begin();vecin!=v[x].end();++vecin)
        if(!viz[*vecin]) dfs1(*vecin);
    postordine[++k]=x;
}
void dfs(int x)
{
    Sol[culoare].push_back(x);
    cul[x]=culoare;
    for(vector<int>::iterator vecin=vt[x].begin();vecin!=vt[x].end();++vecin)
        if(!cul[*vecin]) dfs(*vecin);
}
int main()
{
    int x,y;
    fin>>N>>M;
    for(int i=1;i<=M;++i)
    {
        fin>>x>>y;
        v[x].push_back(y);
        vt[y].push_back(x);
    }
    for(int i=1;i<=N;++i)
        if(!viz[i]) dfs1(i);
    for(int i=N;i>=1;i--)
        if(cul[postordine[i]]==0)
        {
            culoare++;
            dfs(postordine[i]);
        }
    fout<<culoare<<"\n";
    for(int i=1;i<=culoare;++i)
    {
        for(vector<int>::iterator it=Sol[i].begin();it!=Sol[i].end();++it)
            fout<<*it<< " ";
        fout<<"\n";
    }
    return 0;
}