#include<cstdio>
#include<vector>
#include<bitset>
using namespace std;
const int NMAX = 100005;
int n,m,i,j,x,y,TSort[NMAX],N,cnt;
vector<int> Graph[NMAX],Transpose_Graph[NMAX],Components[NMAX];
bitset<NMAX> viz;
void Read()
{
    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);
        Graph[x].push_back(y);
        Transpose_Graph[y].push_back(x);
    }
}
void DFS(int x)
{
    viz[x]=1;
    for(vector<int>::iterator it=Graph[x].begin();it!=Graph[x].end();it++)
        if(!viz[*it]) DFS(*it);
    TSort[++N]=x;
}
void DFST(int x)
{
    viz[x]=0; Components[cnt].push_back(x);
    for(vector<int>::iterator it=Transpose_Graph[x].begin();it!=Transpose_Graph[x].end();it++)
        if(viz[*it]) DFST(*it);
}
void Kosaraju()
{
    for(i=1;i<=n;i++)
        if(!viz[i]) DFS(i);
    for(i=N;i;i--)
        if(viz[TSort[i]]) {cnt++; DFST(TSort[i]);}
}
void Print()
{
    printf("%d\n",cnt);
    for(i=1;i<=cnt;i++)
    {
        for(vector<int>::iterator it=Components[i].begin();it!=Components[i].end();it++)
            printf("%d ",*it);
        printf("\n");
    }
}
int main()
{
    Read();
    Kosaraju();
    Print();
    return 0;
}