#include <cstdio>
#include <vector>
using namespace std;
int n,m,x,y,t[100005],ct,ct1;
bool viz[100005];
vector <int>V1[100005],V2[100005],VS[100005];
void DFS(int nod)
   {int i;
   viz[nod]=1;
    for(i=0;i<V1[nod].size();i++)
       {if(viz[V1[nod][i]]==0)DFS(V1[nod][i]);
       }ct++;
       t[ct]=nod;
   }
void DFSt(int nod)
   {int i;
    viz[nod]=1;
    VS[ct1].push_back(nod);
    for(i=0;i<V2[nod].size();i++)
       {if(viz[V2[nod][i]]==0)DFSt(V2[nod][i]);
       }
   }
int main()
{int i,j;
 freopen("ctc.in","r",stdin);
 freopen("ctc.out","w",stdout);
 scanf("%d%d",&n,&m);
 for(i=1;i<=m;i++)
    {scanf("%d%d",&x,&y);
     V1[x].push_back(y);
     V2[y].push_back(x);
    }
 for(i=1;i<=n;i++)
 {if(viz[i]==0)DFS(i);
 }
 for(i=1;i<=n;i++)
    viz[i]=0;
 ct1=0;
 for(i=ct;i>=1;i--)
    {//printf("%d ",t[i]);
     if(viz[t[i]]==0){ct1++;DFSt(t[i]);}
    }
    printf("%d\n",ct1);
for(i=1;i<=ct1;i++)
    {for(j=0;j<VS[i].size();j++)
        printf("%d ",VS[i][j]);
    printf("\n");
    }
}