#include <iostream>
#include <fstream>
#include <vector>
#define nmax 100001
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
int V[nmax],P[nmax],k,n,m;
vector <int> M[nmax];
vector <int> T[nmax];
vector <int> R[nmax];
void dfs(int nod){
    V[nod]=1;
    for(vector<int>::iterator it=M[nod].begin();it!=M[nod].end();it++){
        if(!V[*it]){
            dfs(*it);
        }
    }
    P[++k]=nod;
}
void dfss(int nod){
    R[k].push_back(nod);V[nod]=0;
    for(vector<int>::iterator it=T[nod].begin();it!=T[nod].end();it++){
        if(V[*it]){
            dfss(*it);
        }
    }
}
int main()
{
    f>>n>>m;int x,y;
    while(m--){
        f>>x>>y;
        M[x].push_back(y);
        T[y].push_back(x);
    }
    for(int i=1;i<=n;i++){
        if(!V[i]){
            dfs(i);
        }
    }k=0;
    for(int i=n;i>=1;i--){
        if(V[P[i]]){
            dfss(P[i]);
            k++;
        }
    }
    g<<k<<endl;
    for(int i=0;i<k;i++){
        for(int j=0;j<R[i].size();j++){
            g<<R[i][j]<<" ";
        }g<<endl;
    }
    return 0;
}