#include <iostream>
#include <fstream>
#include <vector>
#include <cstring>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
#define MAX 100001
vector <int> G[MAX], Gt[MAX], ans;
vector < vector <int> > rez;
typedef vector <int> ::iterator iter;
int s[MAX], dr;
bool viz[MAX];

void df1(int nod)
{
    if(viz[nod])
        return;
    viz[nod]=1;
    for(iter it=G[nod].begin();it!=G[nod].end();it++)
    {
        df1(*it);
    }
    s[++dr]=nod;
}

void df2(int nod)
{
    if(viz[nod])
        return;
    viz[nod]=1;
    ans.push_back(nod);
    for(iter it=Gt[nod].begin();it!=Gt[nod].end();it++)
    {
        df2(*it);
    }
}

int main()
{
    int n, m, x, y, i;
    fin>>n>>m;
    while(m--)
    {
        fin>>x>>y;
        G[x].push_back(y);
        Gt[y].push_back(x);
    }
    for(i=1;i<=n;i++)
        df1(i);
    memset(viz, 0, sizeof(viz));
    while(dr)
    {
        x=s[dr];
        dr--;
        if(viz[x])
            continue;
        ans.clear();
        df2(x);
        rez.push_back(ans);
    }
    fout<<rez.size()<<"\n";
    while(rez.size())
    {
        for(iter it=rez[rez.size()-1].begin();it!=rez[rez.size()-1].end();it++)
        {
            fout<<*it<<" ";
        }
        fout<<"\n";
        rez.pop_back();
    }
}