#include <cstdio>
#include <vector>
#include <algorithm>
#define N 100010
using namespace std;
vector<int>s,c,v[N];
vector<vector<int> >C;
int n,x,y,m,k,nc,viz[N],back[N],i;
void df(int nod)
{
    viz[nod]=++k;
    back[nod]=k;
    s.push_back(nod);
    for(vector<int>::iterator it=v[nod].begin();it!=v[nod].end();it++)
    {
        if(!viz[*it])
            df(*it);
        if(viz[*it]>0)
            back[nod]=min(back[nod],back[*it]);
    }
    if(viz[nod]==back[nod])
    {
        c.resize(0);
        do
        {
            c.push_back(s.back());
            viz[s.back()]=-1;
            s.pop_back();
        }
        while(c.back()!=nod);
        C.push_back(c);
        nc++;
    }
}
int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(;m;m--)
    {
        scanf("%d%d",&x,&y);
        v[x].push_back(y);
    }
    for(i=1;i<=n;i++)
    {
        if(!viz[i])
            df(i);
    }
    printf("%d\n",nc);
    for(i=0;i<nc;i++)
    {
        for(vector<int>::iterator it=C[i].begin();it!=C[i].end();it++)
            printf("%d ",*it);
        printf("\n");
    }
    return 0;
}