#include<cstdio>
#include<vector>
#include<deque>
using namespace std;
int n,m,i,k,l,x,y,viz[100001],ord[100001];
vector<int>v[100001],t[100001],sol[100001];
deque<int>d,q;

void df1(int x)
{
    int j;
    viz[x]=1;
    for(j=0;j<v[x].size();j++)if(viz[v[x][j]]==0)df1(v[x][j]);
    k++,ord[k]=x;
}

void df(int x)
{
    int j;
    viz[x]=1;
    sol[k].push_back(x);
    for(j=0;j<t[x].size();j++)if(viz[t[x][j]]==0)df(t[x][j]);
}

void re()
{
    for(i=1;i<=n;i++)if(viz[i]==0)df1(i);
    for(i=1;i<=n;i++)viz[i]=0;
    k=0;
    for(i=n;i>=1;i--)if(viz[ord[i]]==0)k++,df(ord[i]);
}

void citire()
{
    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),v[x].push_back(y),t[y].push_back(x);
}

void afisare()
{
    int j;
    printf("%d\n",k);
    for(i=1;i<=k;i++){
      for(j=0;j<sol[i].size();j++)printf("%d ",sol[i][j]);
        printf("\n");
          }
}

int main()
{
    citire();
    re();
    afisare();
    return 0;
}