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

using namespace std;

vector <int> L[Nmax],T[Nmax],Comp[Nmax];
bool seen[Nmax];
int order[Nmax],l,nr_comp,n;

inline void dfs(int nod)
{
    seen[nod]=1;
    for(auto it : L[nod])
        if(!seen[it]) dfs(it);
    order[++l]=nod;
}

inline void dfs1(int nod)
{
    seen[nod]=0;
    Comp[nr_comp].pb(nod);
    for(auto it : T[nod])
        if(seen[it]) dfs1(it);
}

int main()
{
    int m,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(!seen[i]) dfs(i);

    for(i=n;i;--i)
        if(seen[order[i]])
        {
            ++nr_comp;
            dfs1(order[i]);
        }

    cout<<nr_comp<<"\n";
    for(i=1;i<=nr_comp;++i)
    {
        for(auto it : Comp[i]) cout<<it<<" ";
        cout<<"\n";
    }
    return 0;
}