#include <bits/stdc++.h>
#define pb push_back
#define Nmax 100005

using namespace std;

vector <int> L[Nmax],T[Nmax],Ctc[Nmax];
bool viz[Nmax],used[Nmax];
int v[Nmax],l,nrCtc;

inline void Dfs(int nod)
{
    viz[nod]=1;
    for(auto it : L[nod])
        if(!viz[it]) Dfs(it);
    v[++l]=nod;
}

inline void Dfs1(int nod)
{
    used[nod]=1; Ctc[nrCtc].pb(nod);
    for(auto it : T[nod])
        if(!used[it]) Dfs1(it);
}

int main()
{
    int m,n,x,y,i;
    ifstream cin("ctc.in");
    ofstream cout("ctc.out");
    cin>>n>>m;
    while(m--)
    {
        cin>>x>>y;
        L[x].pb(y); T[y].pb(x);
    }
    for(i=1;i<=n;++i)
        if(!viz[i]) Dfs(i);
    for(i=n;i;--i)
        if(!used[v[i]])
        {
            ++nrCtc;
            Dfs1(v[i]);
        }
    cout<<nrCtc<<"\n";
    for(i=1;i<=nrCtc;++i)
    {
        for(auto it : Ctc[i]) cout<<it<<" ";
        cout<<"\n";
    }
    return 0;
}