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

vector <int> G[lim];
vector <int> c;
vector <vector <int> > C;
stack <int> S;
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 nrcomp = 1;
int fol[lim];
struct comp
{
    int index,lowlink;

}viz[lim];
void tarjan(int i)
{
    viz[i].index = nrcomp;
    viz[i].lowlink = nrcomp;

    nrcomp++;
    S.push(i);
    fol[i] = 1;

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

    if(viz[i].lowlink == viz[i].index)
    {
        int x;
        c.clear();
            do
            {
              x = S.top();
              fol[x] = 0;
              S.pop();
              c.push_back(x);
            }while(x!=i);
        C.push_back(c);
    }
}

void solve()
{
    for(int i=1;i<=n;i++)
        {
            if(!viz[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;
}