#include <cstdio>
#include <vector>
#include <cstring>
#define N 100001
using namespace std;
vector <int> G[N],GT[N],sol[N];
bool viz[N];
int t[N],n,m,k,nr;
void read()
{
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);
   G[x].push_back(y);
   GT[y].push_back(x);
   }
}
void dfs(int node)
{
viz[node]=1;
for (int i=0;i<G[node].size();++i)
    if (!viz[G[node][i]]) dfs(G[node][i]);
t[k++]=node;
}
void dfst(int node)
{
viz[node]=1;
for (int i=0;i<GT[node].size();++i)
    if (!viz[GT[node][i]]) {
                           sol[nr].push_back(GT[node][i]);
                           dfst(GT[node][i]);
                          }
}
void write()
{
int i,j;
freopen("ctc.out","w",stdout);
printf("%d\n",nr);
for (i=0;i<nr;++i)
   {
   for (j=0;j<sol[i].size();++j)
   printf("%d ",sol[i][j]);
   printf("\n");
   }
}
int main()
{
int i;
read();
for (i=1;i<=n;i++)
if (!viz[i]) dfs(i);
memset(viz,0,sizeof(viz));
for (i=n-1;i>0;i--)
    if (!viz[t[i]]) {
                     sol[nr].push_back(t[i]);
                     dfst(t[i]);
                     nr++;
                    }
write();
}