#include <bits/stdc++.h>
using namespace std;
vector <int> v[100001],afis[100001];
bool vis[100001];
int lista[100001];
int cnt;
void dfs(int nod)
{
    vis[nod]=1;
    for(auto it:v[nod])
        if(!vis[it])
            dfs(it);
    lista[++cnt]=nod;
}
void dfsMarc(int nod)
{
    vis[nod]=1;
    afis[cnt].push_back(nod);
    for(auto it:v[nod])
        if(!vis[it])
            dfsMarc(it);
}
int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    int n,m,i,a,b;
    cin>>n>>m;
    for(i=1;i<=m;i++)
    {
        cin>>a>>b;
        v[a].push_back(b);
    }
    for(i=1;i<=n;i++)
        if(!vis[i])
            dfs(i);
    for(i=1;i<=n;i++)
        vis[i]=0;
    cnt=0;
    for(i=1;i<=n;i++)
        if(!vis[lista[i]])
        {
            cnt++;
            dfsMarc(lista[i]);
        }
    cout<<cnt<<'\n';
    for(i=1;i<=cnt;i++)
    {
        for(auto it:afis[i])
            cout<<it<<" ";
        cout<<'\n';
    }
    return 0;
}