#include <fstream>
#include <bitset>
#include <vector>
#include <deque>
#define dim 100001
using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

int n,m,i,j,cnt,lvl,niv[dim],low[dim],x;
vector <int> l[dim];
bitset <dim> f;
vector <int> c[dim];
deque <int> q;

void dfs(int nod){
    lvl++;
    niv[nod]=lvl;
    low[nod]=lvl;
    q.push_back(nod);
    f[nod]=1;

    for(int i=0;i<l[nod].size();i++){
        int vec=l[nod][i];

        if(niv[vec]==0){
            dfs(vec);
            low[nod]=min(low[nod],low[vec]);
        }else{
            if(f[vec])
                low[nod]=min(low[nod],niv[vec]);
        }
    }

    if(low[nod]==niv[nod]){
        cnt++;

        do{
            x=q.back();
            c[cnt].push_back(x);
            f[x]=0;
            q.pop_back();
        }while(x!=nod);
    }
}

int main(){
    fin>>n>>m;

    for(;m;m--){
        fin>>i>>j;
        l[i].push_back(j);
    }

    for(i=1;i<=n;i++)
        if(niv[i]==0)
            dfs(i);

    fout<<cnt<<"\n";
    for(i=1;i<=cnt;i++,fout<<"\n")
        for(j=0;j<c[i].size();j++)
            fout<<c[i][j]<<" ";

    return 0;
}