#include <vector>
#include <algorithm>
#include <fstream>
using namespace std;
ifstream fin("lant2.in");
ofstream gout("lant2.out");
vector<int>g[100001],gt[100001];
vector<int>post;
bool *viz;
void dfs(int i)
{
    viz[i]=1;
    for(int j:g[i])if(!viz[j])dfs(j);
    post.push_back(i);
}
void dfsT(int i,vector<int>&d)
{
    d.push_back(i);
    viz[i]=1;
    for(int j:gt[i])if(!viz[j])dfsT(j,d);
}
int main()
{
    ios_base::sync_with_stdio(false);
    fin.tie(0);
    gout.tie(0);
    int n,m,i,j;
    fin>>n>>m;
    viz=new bool[n+1];
    fill(viz+1,viz+n+1,0);
    while(m--)
    {
        fin>>i>>j;
        g[i].push_back(j);
        gt[j].push_back(i);
    }
    vector<vector<int>>ans;
    for(i=1; i<=n; ++i)if(!viz[i])dfs(i);
    fill(viz+1,viz+n+1,0);
    for(auto it=post.rbegin(); it!=post.rend(); ++it)if(!viz[*it])
        {
            ans.push_back(vector<int>(0));
            dfsT(*it,ans.back());
        }
    sort(ans.begin(),ans.end(),[](const vector<int>&d1,const vector<int>&d2)->bool{return d1[0]<d2[0];});
    gout<<ans.size()<<'\n';
    for(auto p:ans)
    {
        sort(p.begin(),p.end());
        for(auto o:p)gout<<o<<' ';
        gout<<'\n';
    }
    return 0;
}