#include <bits/stdc++.h>
#include <fstream>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
const int NMAX = 100010;
vector<pair<int,bool>> graf[NMAX];
bool viz[NMAX];
bool vizPlus[NMAX],vizMinus[NMAX];
vector<vector<int>> comps;
void dfsPlus(int node)
{
    for(int i = 0; i<graf[node].size(); i++)
    {
        if(!vizPlus[graf[node][i].first]&&graf[node][i].second)
        {
            vizPlus[graf[node][i].first] = true;
            dfsPlus(graf[node][i].first);
        }
    }
}
void dfsMinus(int node)
{
    for(int i = 0; i<graf[node].size(); i++)
    {
        if(!vizMinus[graf[node][i].first]&&!graf[node][i].second)
        {
            if(vizPlus[graf[node][i].first])
            {
                comps[comps.size()-1].push_back(graf[node][i].first);
                viz[graf[node][i].first] = true;
            }
            vizMinus[graf[node][i].first]=true;
            dfsMinus(graf[node][i].first);
        }
    }
}
void getComp(int node)
{
    fill(vizPlus,vizPlus+NMAX,false);
    fill(vizMinus,vizMinus+NMAX,false);

    vector<int> v;
    v.push_back(node);
    comps.push_back(v);
    vizPlus[node]=true;
    dfsPlus(node);
    vizMinus[node]=true;
    dfsMinus(node);
}
int main()
{
    ios::sync_with_stdio(0);
    fin.tie(0);
    fout.tie(0);
    int n,m;
    fin>>n>>m;
    for(int i = 0; i<m; i++)
    {
        int x,y;
        fin>>x>>y;
        graf[x].push_back({y,true});
        graf[y].push_back({x,false});
    }
    for(int i = 1; i<=n; i++)
    {
        if(!viz[i])
        {
            getComp(i);
        }
    }
    fout<<comps.size()<<'\n';
    for(vector<int> v:comps)
    {
        for(int i:v)
            fout<<i<<" ";
        fout<<'\n';
    }
    return 0;
}