//#include <iostream>
#include <bits/stdc++.h>
using namespace std;
ifstream in("ctc.in");
ofstream out("ctc.out");
const int Max=100005;
bool viz[Max]; int n,m,nr;
stack <int>s;
vector <int>v[Max],vt[Max],ctc[Max];
void dfs(int nod)
{
    viz[nod]=1;
    for(int j=0;j<v[nod].size();j++)
    {
        int vecin=v[nod][j];
        if(!viz[vecin])
            dfs(vecin);
    }
    s.push(nod);
}
void dfs2(int nod)
{
    viz[nod]=0;
    for(int j=0;j<vt[nod].size();j++)
    {
        int vecin=vt[nod][j];
        if(viz[vecin])
            dfs2(vecin);
    }
    ctc[nr].push_back(nod);
}
void citire()
{
   in>>n>>m;
   for(int i=1;i<=m;i++)
   {
       int x,y; in>>x>>y;
       v[x].push_back(y);
       vt[y].push_back(x);
   }
}
int main()
{
    citire();
    dfs(1);
    while(!s.empty())
    {
        int nod=s.top(); s.pop();
        if(viz[nod])
        {
            nr++;
             dfs2(nod);
        }

    }
    out<<nr<<" "<<"\n";
    for(int i=1;i<=nr;i++)
    {
        for(int j=0;j<ctc[i].size();j++)
            out<<ctc[i][j]<<" ";
        out<<"\n";
    }
    return 0;
}