#include <bits/stdc++.h>
#define Dmax 100005

using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
int n,m,nrCTC;
stack<int>S;
vector<int>G[Dmax],GT[Dmax],CTC[Dmax];
bool viz1[Dmax],viz2[Dmax];

void DFS1(int nod)
{
    viz1[nod] = true;
    for(vector<int>::iterator it = G[nod].begin(); it < G[nod].end(); it++)
    {
        int Vecin = *it;
        if(!viz1[Vecin])
            DFS1(Vecin);
    }
    S.push(nod);
}

void DFS2(int nod)
{
    viz2[nod] = true;
    for(vector<int>::iterator it = GT[nod].begin(); it < GT[nod].end(); it++)
    {
        int Vecin = *it;
        if(!viz2[Vecin])
            DFS2(Vecin);
    }
    CTC[nrCTC].push_back(nod);
}

int main()
{
    f>>n>>m;
    for(int i = 1; i <= m; i++)
    {
        int x,y;
        f>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    for(int i = 1; i <= n; i++)
        if(!viz1[i])
            DFS1(i);
    while(!S.empty())
    {
        if(!viz2[S.top()])
        {
            nrCTC++;
            DFS2(S.top());
        }
    S.pop();
    }
sort(CTC+1,CTC+1+nrCTC);
for(int i = 1; i <= nrCTC; i++)
    sort(CTC[i].begin(),CTC[i].end());
g<<nrCTC<<"\n";
    for(int i = 1; i <= nrCTC; i++,g<<"\n")
        for(vector<int>::iterator it = CTC[i].begin(); it < CTC[i].end(); it++)
        g<<*it<<" ";
    return 0;
}