#include <fstream>
#include <vector>
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
vector <int> a[100001],b[100001],c[100001];
int d[100001],i,n,m,x,y,nr,j,viz[100001],p;
void dfs(int nod)
{
    int i;
    viz[nod]=1;
    for(i=0;i<a[nod].size();i++)
    {
        if(viz[a[nod][i]]==0)
            dfs(a[nod][i]);
    }
    d[++p]=nod;
}
void dfs1(int nod)
{
    viz[nod]=0;
    c[nr].push_back(nod);
    for(int i=0;i<b[nod].size();i++)
        if(viz[b[nod][i]]==1)
            dfs1(b[nod][i]);
}
int main()
{f>>n>>m;
    for(i=1;i<=m;i++){
           f>>x>>y;
        a[x].push_back(y);
        b[y].push_back(x);

    }
    for(i=1; i<=n; i++)
        if(viz[i]==0)
            dfs(i);
    nr=0;
    for(i=n;i>=1;i--)
        if(viz[d[i]]==1)
        {
            nr++;
            dfs1(d[i]);
        }
    g<<nr<<'\n';
    for(i=1;i<=nr;i++)
    {
        for(int j=0;j<c[i].size();j++)
            g<<c[i][j]<<" ";
        g<<"\n";
    }


    return 0;
}