#include <iostream>
#include<fstream>
#include<vector>
#include<queue>
#define mx 100001
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
vector<int> v1[mx],v2[mx],sol[mx];
bool viz[mx];
int n,m,p[mx],cnt,nr;
void citire()
{
    int i,x,y;
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>x>>y;
        v1[x].push_back(y);
        v2[y].push_back(x);
    }
}
void dfs(int nod)
{
    viz[nod]=true;
    for(unsigned int i=0;i<v1[nod].size();++i)
        if(viz[v1[nod][i]]==false)
        dfs(v1[nod][i]);
    cnt++;
    p[cnt]=nod;
}
void dfs2(int nod)
{
    viz[nod]=false;
    sol[nr].push_back(nod);
    for(unsigned int i=0;i<v2[nod].size();++i)
        if(viz[v2[nod][i]]==true)
        dfs2(v2[nod][i]);
}
int main()
{
    citire();
    for(int i=1;i<=n;i++)
    if(!viz[i])
    dfs(i);
    for(int i=n;i>=1;i--)
    {
        if(viz[p[i]])
        {
            nr++;
        dfs2(p[i]);}
    }
    fout<<nr<<'\n';
    for(int i=1;i<=nr;i++)
    {
        for(unsigned int j=0;j<sol[i].size();++j)
            fout<<sol[i][j]<<" ";
        fout<<'\n';
    }
       return 0;
}