#include <bits/stdc++.h>
#define inf 2000000

using namespace std;

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

int n,m;
vector<int>L[100002],LT[100002];
bool viz[100002];
stack<int>S;
vector<int>ctc[100002];
void DFS(int nod)
{
    viz[nod]=1;

    for(auto it : L[nod])
    {
        if(viz[it]==0)
            DFS(it);
    }
    S.push(nod);
}

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

void Kosaraju(int & cnt)
{
    for(int i=1;i<=n;++i)
    {
        if(viz[i]==0)
            DFS(i);
    }
    for(int i=1;i<=n;++i)
        viz[i]=0;
    while(!S.empty())
    {
        int nod=S.top();
        S.pop();
        if(viz[nod]==0)
        {
            DFS2(nod,++cnt);
        }
    }
}
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);
    }
    int cnt=0;
    Kosaraju(cnt);

    fout<<cnt<<'\n';

    for(int i=1;i<=cnt;++i,fout<<'\n')
        for(auto it : ctc[i])
            fout<<it<<' ';


}