#include<cstdio>
#include<stack>
#include<vector>
#include<algorithm>
#define min(a,b) (a<b?a:b)
#define NMAX 100005
using namespace std;
stack<int>st;
vector<int>v[NMAX],sol[NMAX];
int g,n,m,x,y,nr,i;
int viz[NMAX],niv[NMAX],low[NMAX];
void DF(int nod)
{
    st.push(nod);viz[nod]=1;
    niv[nod]=low[nod]=++g;
    vector<int>::iterator it;
    for (it=v[nod].begin();it!=v[nod].end();++it)
    {
        if (niv[*it]==0)
        {
            DF(*it);
            low[nod]=min(low[*it],low[nod]);
        }
        else if (viz[*it]==1) low[nod]=min(low[*it],low[nod]);
    }
    if (niv[nod]==low[nod])
    {
        ++nr;
        do
        {
            x=st.top();
            sol[nr].push_back(x);
            viz[x]=0;
            st.pop();
        }while(x!=nod);
    }
}
int main()
{
    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);
    }
    for(i=1;i<=n;++i)
        if (niv[i]==0) DF(i);
    for(i=1;i<=nr;++i)
        sort(sol[i].begin(),sol[i].end());
    printf("%d\n",nr);
    for (i=1;i<=nr;++i)
    {
        vector<int>::iterator it;
        for (it=sol[i].begin();it!=sol[i].end();++it)
        {
            printf("%d ",*it);
        }
        printf("\n");
    }
    return 0;
}