#include <fstream>
#include <vector>
using namespace std;

ifstream in("ctc.in");
ofstream out("ctc.out");

const int N=100005;
vector <int> graf[N], trans[N], sol[N];
int nr,n,m,t[N];
bool use[N],viz[N];

void dfsgraf(int x)
{
    use[x]=true;
    for(vector<int> :: iterator it=graf[x].begin();it!=graf[x].end();it++)
        if(!use[*it])
            dfsgraf(*it);
    t[++nr]=x;
}

void dfstrans(int x,int num)
{
    sol[num].push_back(x);
    viz[x]=true;
    for(vector<int> :: iterator it=trans[x].begin();it!=trans[x].end();it++)
        if(!viz[*it])
            dfstrans(*it,num);
}

int main()
{
    int x,y;
    int num=0;
    in>>n>>m;

    while(m--)
    {
        in>>x>>y;
        graf[x].push_back(y);
        trans[y].push_back(x);
    }

    for(int i=1;i<=n;i++)
        if(!use[i])
            dfsgraf(i);

    for(int i=nr;i>=0;i--)
        if(!viz[t[i]])
            dfstrans(t[i],++num);

    out<<--num<<"\n";

    for(int i=1;i<=num;i++)
    {
        for(vector <int> :: iterator it=sol[i].begin();it!=sol[i].end();it++)
            out<<(*it)<<" ";
        out<<"\n";
    }

    return 0;
}