#include <fstream>
#include <cstdio>
#include <vector>
#define Nmax 100001
using namespace std;

ofstream g("ctc.out");

int n,m;
bool rep[Nmax],uz[Nmax];
vector<int> V[Nmax],C,rez[Nmax],V2[Nmax];

void dfP(int nod)
{
    uz[nod] = 1;
    for (int i=0;i<V[nod].size();i++)
    {
        if (!uz[V[nod][i]])
            dfP(V[nod][i]);
    }
    C.push_back(nod);
}

void dfM(int nod,int root)
{
    rep[nod] = 1;
    rez[root].push_back(nod);
    for (int i=0;i<V2[nod].size();i++)
        if (!rep[V2[nod][i]])
            dfM(V2[nod][i],root);
}

int main()
{
    freopen("ctc.in","r",stdin);
    scanf("%d%d",&n,&m);

    for (int i=1;i<=m;i++)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        V[x].push_back(y);
        V2[y].push_back(x);
    }

    for (int i=1;i<=n;i++)
    {
        if (!uz[i])
            dfP(i);
    }

    int nr=0;
    while (!C.empty())
    {
        if (!rep[C.back()])
        {
            nr++;
            dfM(C.back(),C.back());
        }
        C.pop_back();
    }

    g<<nr<<'\n';
    for (int i=1;i<=n;i++)
        if (rez[i].size()!=0)
        {
            for (int j=0;j<rez[i].size();j++)
                g<<rez[i][j]<<' ';
            g<<"\n";
        }

    return 0;
}