#include <fstream>
#include <vector>;
#define nmax 100005
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
vector <int> v[nmax];
vector <int> sol[nmax];
int nrc,n,m,x,y,index,onstack[nmax],idx[nmax],lowlink[nmax],s[nmax],sz;
void tarjan(int nod)
{
    int i,vec;
    onstack[nod]=1;
    idx[nod]=++index;
    lowlink[nod]=index;
    s[++sz]=nod;
    for(i=0;i<v[nod].size();i++)
    {
        vec=v[nod][i];
        if(!idx[vec])
        {
            tarjan(vec);
            lowlink[nod]=min(lowlink[nod],lowlink[vec]);
        }
        else if(onstack[vec]) lowlink[nod]=min(lowlink[nod],lowlink[vec]);
    }
    if(idx[nod]==lowlink[nod])
    {
        nrc++;
        do
        {
            x=s[sz]; onstack[x] = 0;
            sol[nrc].push_back(x);
            sz--;
        }while(x!=nod);
    }
}
int main()
{
    int i,j;
    f>>n>>m;
    for(i=1;i<=m;i++)
    {
        f>>x>>y;
        v[x].push_back(y);
    }
    for(i=1;i<=n;i++)
        if(!idx[i]) tarjan(i);
        g<<nrc<<'\n';
        for(i=1;i<=nrc;i++)
        {
            for(j=0;j<sol[i].size();j++)
                g<<sol[i][j]<<' ';
                g<<'\n';
        }
    return 0;
}