#include <fstream>
#include <vector>
#include <cstring>
#include <stack>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int n,m,nr,nrc,niv[100001],minlv[100001];
vector<int>v[100001],cc[100001];
bool instiva[100001];
stack<int>s;
int nv;
void dfs(int k){
    nv++;
    niv[k]=minlv[k]=nv;
    s.push(k);
    instiva[k]=1;
    for(auto i:v[k]){
        if(niv[i]!=0){
            if(instiva[i]==1)  /// am muchie de intoarcere
                    minlv[k]=min(minlv[k],niv[i]);

        }else{
              dfs(i);
              if(instiva[i]==1)
              minlv[k]=min(minlv[k],minlv[i]);

        }
    }
    if(niv[k]==minlv[k]&&instiva[k]==1){   /// gasii comp tare conexa
            nrc++;
            while(s.top()!=k){
                cc[nrc].push_back(s.top());
                instiva[s.top()]=0;
                s.pop();
            }
            cc[nrc].push_back(k);
            instiva[k]=0;
            s.pop();

    }

}
int main()
{
    fin>>n>>m;
    int x,y;
    for(int i=1;i<=m;i++){
        fin>>x>>y;
        v[x].push_back(y);

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

    fout<<nrc<<'\n';
    for(int i=1;i<=nrc;i++){
        for(auto j:cc[i])
            fout<<j<<" ";
        fout<<'\n';
    }
    return 0;
}