#include <cstdio>
#include <vector>
#define lim 100010
#include <stack>
using namespace std;

vector <int> G[lim];
vector <int> c;
vector < vector<int> > C;
stack <int> S;

struct comp
{
        int index,lowlink;
}v[lim];
int n,m;
void citire()
{
    scanf("%d %d",&n,&m);
        for(int i=0;i<m;i++)
            {   int x,y;
                scanf("%d %d",&x,&y);
                G[x].push_back(y);
            }
}

int lg = 1;
int viz[lim];

void tarjan(int i)
{
    v[i].index = lg;
    v[i].lowlink = lg;
    lg++;
    S.push(i);
    viz[i] = 1;

    for(int ngh=0;ngh<G[i].size();ngh++)
    {
            if(!v[G[i][ngh]].index)
            {
                tarjan(G[i][ngh]);
                v[i].lowlink = min (v[i].lowlink, v[G[i][ngh]].lowlink);
            }
            else
                if(viz[G[i][ngh]])
                v[i].lowlink = min (v[i].lowlink, v[G[i][ngh]].lowlink);

    }

    if(v[i].index == v[i].lowlink)
    {   int x;
        c.clear();
        do{

            x = S.top();
            S.pop();
            c.push_back(x);
            viz[x] = 0;
        }while(i!=x);
        C.push_back(c);
    }

}

void solve()
{
    for(int i=1;i<=n;i++)
        {
          if(!v[i].index)
            {
                tarjan(i);
            }
        }
    printf("%d\n",C.size());
    for(int i=0;i<C.size();i++)
    {
        for(int j=0;j<C[i].size();j++)
            {
                printf("%d ",C[i][j]);
            }
        printf("\n");
    }


}

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    citire();
    solve();
    return 0;
}