#include <bits/stdc++.h>
#define NM 100010
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
vector <int> g[NM],gt[NM],ctc[NM];
int x,y,i,n,m,cnt,viz[NM];
stack <int> s;
void dfs(int nod)
{
    viz[nod]=1;
    for(auto it:g[nod])
        if(viz[it]==0)
            dfs(it);
    s.push(nod);
}
void dfsgt(int nod)
{

    viz[nod]=1;
    ctc[cnt].push_back(nod);
    for(auto it:gt[nod])
        if(viz[it]==0)
            dfsgt(it);
}
int main()
{
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>x>>y;
        g[x].push_back(y);
        gt[y].push_back(x);
    }
    for(i=1;i<=n;i++)
        if(viz[i]==0)
            dfs(i);
    memset(viz,0,sizeof(viz));
    while(!s.empty())
    {
        x=s.top();
        s.pop();
        if(viz[x])
            continue;
        cnt++;
        dfsgt(x);
    }    
    fout<<cnt<<'\n';
    for(i=1;i<=n;i++)
    {
        for(auto it:ctc[i])
            fout<<it<<" ";
        fout<<'\n';
    }

}