#include<bits/stdc++.h>
#define Dmax 100005
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
int n,m,ap[Dmax],viz[Dmax],niv[Dmax],nma[Dmax];
vector<int>G[Dmax],sol[Dmax];
int timp,nrCTC;
stack<int>S;


void Tarjan(int nod)
{
    niv[nod]=nma[nod]=++timp;
    viz[nod]=ap[nod]=1;
    S.push(nod);
    for(vector<int>::iterator it = G[nod].begin(); it < G[nod].end(); it++)
    {
        if(!viz[*it])
        {
            Tarjan(*it);
            nma[nod] = min(nma[nod],nma[*it]);
        }else
        if(ap[*it])
            nma[nod] = min(nma[nod],niv[*it]);

    }

    if(nma[nod] == niv[nod])
    {
        nrCTC++;
        while(S.top()!=nod)
        {
            sol[nrCTC].push_back(S.top());
            ap[S.top()] = 0;
            S.pop();
        }
        sol[nrCTC].push_back(S.top());
            ap[S.top()] = 0;
            S.pop();
    }




}

int main()
{
    f>>n>>m;
    for(int i = 1; i <= m; i++)
    {
        int x,y;
        f>>x>>y;
        G[x].push_back(y);
    }
    for(int i = 1; i<= n; i++)
        if(!viz[i])
        Tarjan(i);

    g<<nrCTC<<"\n";
    for(int i = 1; i<=nrCTC; i++,g<<"\n")
            for(vector<int>::iterator it = sol[i].begin(); it < sol[i].end(); it++)
                g<<*it<<" ";


    return 0;
}