#include <iostream>
#include <vector>
#include <stack>
#include <fstream>
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
#define Nmax =10005;
stack <int> s;
vector <int> Mad1[100001],Mad2[100001],cc[100001];
int n,e,nr,a,b,beenthere[100001],p;
void dfs(int nodS)
{int j;
    beenthere[nodS]=1;
    for(int i=0;i<Mad1[nodS].size();++i)
    {
        j=Mad1[nodS][i];
     if(!beenthere[j])
        dfs[j];
    }
    s.push(nodS);
}
void dfst(int nodS)
{int j;
    cc[nr].push_back(nodS);
    beenthere[nodS]=2;
    for(int i=0;i<Mad2[nodS].size();++i)
    {
         j=Mad2[nodS][i];
        if(beenthere[j]==1)
            dfst[i];
    }

}
int main()
{f>>n>>e;
    for(int i=1;i<=e;++i)
    {
        f>>a>>b;
        Mad1[a].push_back(b);
        Mad2[b].push_back(a);

    }
    for(int i=1;i<=n;++i)
    {
        if(!beenthere[i])
            dfs[i];
    }
    while(!s.empty())
    {
        p=s.top();
        if(beenthere[p]==1)
           {
            nr++;
            dfst[p];
           }
        s.pop();
    }
    g<<nr<<endl;
    for(int i=1;i<=nr;++i)
    {
        for(int j=0;j<cc[i].size();++j)
            g<<cc[i][j]<<" ";
        g<<endl;
    }
    return 0;
}