#include <fstream>
#include <vector>
#include <deque>
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
const int N=1e5+5;
int n,m,X,Y;
vector<int>a[N],b[N];
deque<int>st;
bool viz[N];
vector<vector<int>>ans;
vector<int>comp;
void dfs(int nod)
{
    viz[nod]=true;
    for(auto x: a[nod])
        if(viz[x]==0)
            dfs(x);
    st.push_front(nod);

}
void dfs_back(int nod)
{
    viz[nod]=true;
    for(auto x: b[nod])
        if(viz[x]==false)
            dfs_back(x);
    comp.push_back(nod);
}
int main()
{
    f>>n>>m;
    for(int i=1;i<=m;i++)
    {
        f>>X>>Y;
        a[X].push_back(Y);
        b[Y].push_back(X);
    }
    for(int i=1;i<=n;i++)
        if(viz[i]==false)
            dfs(i);
    for(int i=1;i<=n;i++)
        viz[i]=false;
    for(auto x: st)
    {
        if(viz[x]==0)
        {
            comp.clear();
            dfs_back(x);
            ans.push_back(comp);
        }
    }
    g<<ans.size()<<'\n';
    for(auto x: ans)
    {
        for(auto y: x)
            g<<y<<" ";
        g<<'\n';
    }
    return 0;
}