#include <cstdio>
#include <cstring>
#include <fstream>
#include <algorithm>
#include <vector>
#define Nmx 100001

using namespace std;

int n,m,nr,nrs,viz[Nmx],prec[Nmx*2];
struct nod
{
    int inf;
    nod *urm;
};
nod *G[Nmx],*GT[Nmx];
vector<int> sol[Nmx];

ifstream fin("ctc.in");

void add(int x,int y)
{
    nod *aux=new nod;
    aux->inf = y;
    aux->urm = G[x];
    G[x]=aux;
}

void addt(int x,int y)
{
    nod *aux=new nod;
    aux->inf = y;
    aux->urm = GT[x];
    GT[x]=aux;
}


void read()
{
    int x,y;
    fin>>n>>m;
    for(int i=1;i<=m;++i)
    {
        fin>>x>>y;
        add(x,y);
        addt(y,x);
    }
}

void dfs(int x)
{
    viz[x]=1;
    for(nod *p=G[x];p;p=p->urm)
        if(!viz[p->inf])
            dfs(p->inf);
    prec[++nr]=x;
}

void dfst(int x)
{
    viz[x]=0;
    sol[nrs].push_back(x);
    for(nod *p=GT[x];p;p=p->urm)
        if(viz[p->inf])
            dfst(p->inf);
}

void solve()
{
    for(int i=1;i<=n;++i)
        if(!viz[i])
            dfs(i);
    for(int i=nr;i>=1;--i)
        if(viz[prec[i]])
        {
            ++nrs;
            dfst(prec[i]);
        }
    printf("%d\n",nrs);
    for(int i=1;i<=nrs;++i)
    {
        for(int j=0;j<sol[i].size();++j)
            printf("%d ",sol[i][j]);
        printf("\n");
    }
}

int main()
{
    freopen("ctc.out","w",stdout);
    read();
    solve();
    return 0;
}