#include <fstream>
#include <vector>
using namespace std;
ifstream cin("ctc.in");
ofstream cout("ctc.out");
vector <int> g[100001],gi[100001],rez[100001];
int l[100001],ok[100001],t,k;
void dfs1(int nod)
{
    ok[nod]=1;
    for(auto x : gi[nod])
    {
        if(ok[x]==0)
            dfs1(x);
    }
    l[++t]=nod;
}
void dfs2(int nod)
{
    ok[nod]=0;
    rez[k].push_back(nod);
    for(auto x : g[nod])
    {
        if(ok[x]==1)
            dfs2(x);
    }
}
int main()
{
    int n,m,i,x,y;
    cin>>n>>m;
    for(i=1;i<=m;i++)
    {
        cin>>x>>y;
        g[x].push_back(y);
        gi[y].push_back(x);
    }
    for(i=1;i<=n;i++)
    {
        if(ok[i]==0)
            dfs1(i);
    }
    for(i=n;i>=1;i--)
    {
        if(ok[l[i]]==1)
        {
            k++;
            dfs2(l[i]);
        }
    }
    cout<<k<<'\n';
    for(i=1;i<=k;i++)
    {
        for(auto x : rez[i])
            cout<<x<<" ";
        cout<<'\n';
    }
    return 0;
}