#include <bits/stdc++.h>

using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

int n,m;
vector<int>L[100002],LT[100002];
int viz[100002];
int ctc[100002];
vector<int>rasp[100002];
stack<int>S;
void DFS1(int nod)
{
    viz[nod]=1;
    for(auto it : L[nod])
        if(viz[it]==0)
            DFS1(it);

    S.push(nod);
}

void DFS2(int nod,int nr)
{
    ctc[nod]=nr;
    viz[nod]=1;
    for(auto it : LT[nod])
        if(viz[it] == 0)
            DFS2(it,nr);
}

void Kosaraju()
{
    for(int i=1;i<=n;++i)
        if(viz[i]==0)
            DFS1(i);

    for(int i=1;i<=n;++i)
        viz[i]=0;

        int cnt=0;
    while(!S.empty())
    {
        int nod=S.top();
        S.pop();
        if(viz[nod] == 0)
            DFS2(nod,++cnt);
    }
    int nrc=0;
    for(int i=1;i<=n;++i)
    {
        rasp[ctc[i]].push_back(i);
    }

    fout<<cnt<<'\n';

    for(int i=1;i<=cnt;++i)
    {
        for(auto it : rasp[i])
            fout<<it<<' ';

        fout<<'\n';
    }


}

int main()
{
    fin>>n>>m;
    for(int i=1;i<=m;++i)
    {
        int x,y;
        fin>>x>>y;
        L[x].push_back(y);
        LT[y].push_back(x);
    }
    Kosaraju();
    return 0;
}